Front Cover
 Table of Contents
 Back Cover

Group Title: Technical publication R8-TP
Title: A guide for prescribed fire in southern forests
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00001593/00001
 Material Information
Title: A guide for prescribed fire in southern forests
Series Title: Technical publication R8-TP
Physical Description: iv, 56 p. : ill. (some col.), forms, map ; 28 cm.
Language: English
Creator: Wade, Dale D
Lunsford, James D
Dixon, Merlin J
United States -- Forest Service. -- Southern Region
Publisher: U.S. Dept. of Agriculture, Forest Service, Southern Region
Place of Publication: Atlanta Ga
Publication Date: [1989]
Subject: Prescribed burning -- Safety measures -- Handbooks, manuals, etc -- Southern States   ( lcsh )
Forest ecology -- Handbooks, manuals, etc -- Southern States   ( lcsh )
Genre: federal government publication   ( marcgt )
bibliography   ( marcgt )
handbook   ( marcgt )
non-fiction   ( marcgt )
Bibliography: Bibliography: p. 54-56.
Statement of Responsibility: rewritten in 1988 by Dale D. Wade and James D. Lunsford.
General Note: "Originally written in 1966 by Merlin J. Dixon, Southern Region, USDA Forest Service."
General Note: "1973-1979 revisions, lead author Hugh E. Mobley, Southern Region, USDA Forest Service."
General Note: Shipping list no.: 89-149-P.
 Record Information
Bibliographic ID: UF00001593
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: ltqf - AAA0262
notis - AGL5173
alephbibnum - 001353978
oclc - 19668238

Table of Contents
    Front Cover
        Front cover 1
        Front cover 2
        Front cover 3
    Table of Contents
        Page i
        Page ii
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    Back Cover
        Page 58
Full Text

A3./i 6T3,
P, S--rp it

A-- i

t 'I



Applied in a skillful manner
Under exacting weather

* In a definite place
* To achieve specific results

The Objective of this
Prescribed Burning

To help resource managers plan and
execute prescribed burns in Southern
forests by:

* Explaining the reasons for
prescribed burning.
* Emphasizing the environmental
* Explaining the importance of
weather in prescribed burning.

* Describing the various techniques
of prescribed burning.
* Giving general information pertain-
ing to prescribed burning.




Postburn results

Rewritten in 1988 by Dale D. Wade,
Southeastern Forest Experiment
Station; and James D. Lunsford, Fire
Management, Southern Region,
USDA Forest Service
Originally written in 1966 by Merlin J.
Dixon, Southern Region, USDA Forest
1973-1979 revisions, lead author Hugh
E. Mobley, Southern Region, USDA
Forest Service.

Photo assistance was provided by the
Alabama Forestry Commission; Georgia
Forestry Commission; North Carolina
Forest Service; USDI Fish and Wildlife
Service, Piedmont National Wildlife
Refuge; South Carolina Commission of
Forestry; Southeastern Forest Experi-
ment Station, Southern Region, and
Southern Forest Experiment Station,
USDA Forest Service; Tall Timbers
Research Station; Union Camp Cor-
poration; and Westvaco Corporation.

Appreciation is expressed to the
various State and Federal agencies,
private industries and other organiza-
tions for their helpful reviews and

acKing nre in young siasn pine

This guide provides basic information needed to help you become technically proficient in the proper use of
prescribed fire. A glossary toward the end of this manual will help you with unfamiliar terms. bT learn more about
the subject of prescribed fire, a list of suggested reading follows the glossary. Nearby State and Federal resource
management agencies are also excellent sources of information. Many of these agencies provide periodic training in
fire behavior and prescribed fire.


INTRODUCTION .......... ... ........................................ .. ...............
The Ecology of Fire ................ ............... ... ........ . 1
Prescribed Fire History ................... . ................... ... 1
Present Use ...................... ..... ....... .................. 2
Impact of Prescribed Burning .................. ......... ..... . .2
Reduce Hazardous Fuels ............ ........................... 3
Dispose of Logging Debris ..................... ........ ..... . .4
Prepare Sites For Seeding or Planting .............................. .4
Improve Wildlife Habitat .................... ..... ............ 4
Manage Competing Vegetation ............. ................. ... .5
Control Insects and Disease ........................................ 5
Improve Forage For Grazing ............... ........................ 6
Enhance Appearance ................ ............ ............... 6
Improve Access ......................... ....................... 7
Perpetuate Fire-dependent Species .............. ............. . .7

ENVIRONMENTAL EFFECTS ................................. ...... .............. 8
Vegetation ....................... ..... .. ..... ...... 8
Soil ......................................... ................... 9
Water ................... ............... ................ 10
Air ......................... .. ........ . .... ............. 10
Human Health and Welfare ...................................... 11
Wildlife ..................................... .. ............... 11
Aesthetics ......... .................... .................12

WEATHER AND FUEL CONSIDERATIONS ................... . . . ............................ 13
Important Weather Elements .. ........................ ....... .13
Sources of Weather Information .................. ................ 14
Wind ....................... ............................ 14
Underburning ........... ...... .................... ..... ...... 14
Debris burning ............... .................... ....... .... 15
Relative Humidity ............. ..... .. .......................... . 15
Underburning ...................... .................. .. 15
Debris burning ................... ........ ................. 15
Temperature....................... ................... 16
Underburning ............................................... 16
Debris burning ............... ............................. 16
Rainfall and Soil Moisture ........................................16
Underburning .............................................. 16
Debris burning ................. ............................. 16
Fine-Fuel Moisture ..................... ........................ 16
Underburning ............ ............................... 16
Debris burning ........... .............................17
Airmass Stability and Atmospheric Dispersion ......................... 18
Underburning ................ ................... ..... .. 18
Debris burning ................................................18
FIRING TECHNIQUES ............... ...... ..... ................................... 20
General ...................................... .. .. ............. 20
Backing Fire .................... ............. .............. 21
Factors Associated with Backing Fires .......................... . .21


Strip-heading Fire ............................................... 22
Factors Associated with Strip-heading Fires ....................... 22
Flanking Fire ................. .... .......... ...............23
Factors Associated with Flanking Fires ........................... 23
Point Source Fires ....................... ....................24
Factors Associated with Point Source Fires ......................... 25
Aerial Ignition ............................. .............. 25
Factors Associated with Aerial Ignition ............................25
Factors Associated with Ping-pong Ball (DAID) System .................26
Factors Associated with Helitorch System .......................... 26
Center and Circular (Ring) Firing .................. ................. 27
Pile and Windrow Burning ........................................ 27
Factors Associated with Pile and Windrow Burning ................... .28

SMOKE MANAGEMENT ........... .... ......................... .... ..................... 29
Table 1. Relationship of Dispersion Index to On-the-ground
Burning Conditions .............. ........................ 29
Table 2. Effect of Smoke Concentration on Visibility .................. 30
Screening System For Managing Smoke .............. .............30

PLANNING THE PRESCRIBED BURN ................ ........................... ...........33
The Written Plan ................................................. 33
Table 3. Effects of Age of Rough on Some Common Fire Parameters ........ 33
Simple Understory Prescribed Burning Unit Plan ......................... 34
Understory Prescribed Burning Unit Plan ............................. 35
Postharvest Prescribed Burning Unit Plan ......................... 36

PREPARING FOR THE PRESCRIBED BURN ............................. ..................... ..41
Steps to be Considered ................... ............ ............. 41
Establishing Control Lines .......................................... 41
Establishing Control Lines . . . . . . . . . . . .41
After Plow Lines Are Established .............. ................... 41
Burning-unit Map .................................. .......... 41

EXECUTING THE BURN ................... ... ................. .......... ................... 42
Checklist ..................................................... 43

EVALUATING THE BURN ..................... ................................ ...............44
Indications and Guidelines .......................................... 44
Needle Scorch ............. .... ................... ........... 44
Soil and Root Damage .................. ......... .......... 44
Air Quality ...................................................44
Timing and Points to Evaluate ............... . ..................... 45

COORDINATION OF BURNING .................................... .................. ........... 46

RULES OFTHUMB .............. ................... ............................ 48

RED FLAG SITUATIONS ....................... ............. ........................... 49

GLOSSARY ............... .................. ........................... ........ 50

SUGGESTED READING ...................... .............. ............................. 54


el type prior to prescribed burn

Postburn results


The Ecology of Fire
Fire has played a major role in
determining the distribution of plants
across the South. Some plant com-
munities such as cypress swamps sur-
vive for centuries between prolonged
droughts that finally allow stand-
replacement fires to enter. Other com-
munities such as the once vast expanse
of longleaf pine burn every few years.
In fact some ecosystems, for example
the longleaf pine-wiregrass associa-
tion, require periodic fire for their
very survival.
A basic premise of fire ecology is
that wildland fire is neither innately
destructive nor constructive: it simply
causes change. Whether these changes
are viewed as desirable or not depends
upon their compatibility with one's ob-
jectives. Irrespective of man's view-

point, change is biologically necessary
to maintain a healthy ecosystem.
Resource managers have learned to
manipulate fire-caused changes in
plant and animal communities to meet
their needs, and those of humankind in
general, while at the same time preser-
ving underlying natural processes and
functions. They do this by varying the
timing, frequency, and intensity of fire.

Prescribed Fire History
The use of fire in the forests of the
United States has come full cycle. Ear-
ly settlers found Indians using fire in
virgin pine stands and adopted the
practice themselves to provide better
access, improve hunting, and to get rid
of brush and timber so they could
farm. Annual burning to "freshen up"

southern range became a custom. This
practice, plus destructive wildfires
after logging left millions of acres of
forest land in the south devoid of trees.
The increasing wildfire problem
coupled with the need for a fire-free
interval of several years to allow the
pines to become reestablished led
many foresters to advocate the exclu-
sion of all fire from the woods. Others,
however, pointed out that fire might
have a place in the management of
longleaf pine. Fire has been used by
professional foresters to reduce hazar-
dous fuels since the turn of the century.
The misconceptions and controversy
surrounding the deliberate use of fire
to achieve resource management
objectives have slowly been replaced
by facts. As knowledge accumulated,
the use of prescribed fire grew.


t~";rl' :


~4d~-' 1~5.
Lor- '. 1.;*
'C'*- ~

Depression-era photo of unproductive forest land

A I ' I ~I '/'I_- "; - ,; / /


Smoke obscuring highway

Present Use
Today prescribed fire is applied to
roughly 8 million acres in the South
each year about half of which are
burned to achieve various forest
management objectives. Most of the
remainder is for range and agricultural
purposes. Prescribed burning is a
desirable and economically sound
practice on most southern pine sites. In
many cases, prescribed burning is the
only practical choice. Few, if any,
alternative treatments have been
developed that can compete with fire
from the standpoint of effectiveness
and cost. Chemical applications
generally cost more than 10 times as
much per acre as prescribed fire.
Mechanical treatments such as disk-
ing, chopping, or raking are at least 20
times more expensive. Each of these
three alternatives also has associated
environmental costs, such as destruc-
tion of habitat and soil erosion. Both
the probability of causing damage, and
the magnitude of such damage, should
it occur, need to be kept in mind.
In this guide, prescribed burning is
defined as fire applied in a
knowledgeable manner toforestfuels
on a specific land area under selected
weather conditions to accomplish
predetermined, well-defined manage-
ment objectives.

This manual will be most useful in
the lower Piedmont and Coastal Plain.
Prescribed burning in these areas has
been perfected by several generations
of resource managers. Although the
potential of prescribed fire in the upper
Piedmont and mountains of the South
has been demonstrated, few guidelines
exist. If you are interested in the
emerging use of fire in the mountains,
a good source of information and help
is your local State or Federal forestry

Impact of Prescribed
A single prescribed burn can
achieve multiple benefits. For example
a prescribed burn that consumes more
dead fuel than it creates will reduce the
fire hazard and, with few if any
modifications, will also improve
wildlife habitat. Almost any prescribed
burn improves access.
Prescribed fires aren't always
beneficial, however. When conditions
are wrong, prescribed fire can severely
damage the very resource it was in-
tended to benefit. Prescribed fire can
temporarily reduce air quality, but
usually to a much lesser degree than
wildfire. For every prescribed fire op-
portunity, there are tradeoffs that
should be recognized and carefully
weighed before a decision is reached.
Proper planning and execution are

necessary to minimize any detrimental
effects to air quality. Potential off-site
impacts such as downstream water
quality should be carefully considered,
as should on-site impacts to soil and
Public opinion is another factor to
consider because the general public is
concerned about the deterioration of
the environment. Smoke from
prescribed fires, as well as from
wildfires, is highly visible. It is our job
as resource managers to inform the
public of the differences between
prescribed fire and wildfire -which often
look identical to the untrained eye.
Prescribed fire is a complex tool
and should be used only by those trained
in its use. Proper diagnosis and detailed
planning are needed for every area
where burning is contemplated. The
incomplete assessment of any factor
can pose serious liability questions
should the fire escape or its smoke
cause damage. A prescribed fire that
does not accomplish it's intended ob-
jective(s) is a loss of both time and
money, and it may be necessary to
reburn as soon as sufficient fuel ac-
cumulates. Keep in mind that some
resource management objectives can
be met with a single fire, some require
several fires in fairly quick succession,
and some can only be accomplished by
burning periodically throughout the

una ignition

For Prescribed Fire In Forest Resource Management

N Reduce hazardous fuels
0 Prepare sites for seeding and planting
0 Dispose of logging debris
0 Improve wildlife habitat
N Manage competing vegetation
N Control disease
N Improve forage for grazing
a Enhance appearance
0 Improve access
N Perpetuate fire-dependent species 2
" Cycle nutrients o
" Manage endangered species --

Reduce Hazardous
Forest fuels accumulate rapidly in
pine stands on the Coastal Plain. In 5
to 6 years, heavy "roughs" can build
up, posing a serious threat from
wildfire to all forest resources.
Prescribed fire is the most practical
way to reduce dangerous accumula-
tions of combustible fuels under
southern pine stands. Wildfires that
burn into areas where fuels have been
reduced by prescribed burning cause
less damage and are much easier to

control. The appropriate interval be-
tween prescribed burns for fuel reduc-
tion varies with several factors,
including the rate of fuel accumula-
tion, past wildfire occurrence, values
at risk, and the risk of a fire. The time
interval between fires can be as often
as every year although a 3- or 4-year
cycle is usually adequate after the
initial fuel-reduction burn.
The need to reduce hazardous fuel
accumulations in the pine plantations
of the South is increasing. Without fuel
reduction, fire hazard is extremely

high in these vast contiguous stands.
The initial hazard-reduction burn in a
young pine stand requires exacting
conditionsof wind, humidity, and
temperature. Higher wind velocities
and cooler temperatures minimize
scorch damage. Southern pine planta-
tions averaging 10 to 12 feet in height
can be burned by experienced people
under the right conditions without
damage. Young plantations on in-
dustrial lands are often burned for the
first time when they are 15 to 20 feet
tall using aerial ignition; close spacing

Winter backing fire in heavy rough

726 Acrs

0 1 2 3 4 5
Age of Rough (Years)
Annual wildfire acreage depends on age of rough


Damaging wildfire in heavy rough

of ignition spots (e.g., 2 chains by 2
chains), and cool, damp conditions
with some wind are a must to avoid
crown damage.
Subsequent fuel reduction bums
need not cover the entire area. The ob-
jective is to break up fuel continuity.
Fuel reduction on 75 to 80 percent of
the area is sufficient. An added advan-
tage of "patchy" burns is that the un-
burned islands provide cover for
wildlife. These unburned patches will
not have a dangerous accumulation of
fuels at the time of the next burn if they
resulted from a lack of fuel during the
previous fire. If, however, they were
too wet to burn, these islands could
result in a hot spot the next time if a
heading fire was allowed to sweep
through them under appreciably drier
conditions. One reason excessive
crown scorch should be avoided is
because, under some circumstances, it
can add more fuel to the forest floor
than the fire consumed.

Dispose of Logging
After harvest, unmerchantable
limbs and stems are left either scat-
tered across the area or concentrated at
logging decks or delimbing gates,
depending upon the method of logging.
This material is an impediment to both
people and planting equipment. If a
wildfire occurs within the next few
years, fireline construction can be
severely hindered; the result being
larger burn acreages and higher
regeneration losses. Although not all
large material will be consumed by a
prescribed fire, what is left will be ex-
posed so it can be avoided by tractor-
plow operators. In stands that produce
a large amount of cull material, the
debris is often windrowed and burned.
This practice should, however, be
avoided whenever practical because of
smoke management problems and the
potential for site degradation. Broad-
cast burning is generally a much better
alternative. If the debris must be piled
before burning, construct round
"haystack" piles when the debris and
underlying ground are both fairly dry.
This step will limit the amount of dirt
in the pile. Piles containing large
amounts of dirt can seldom be burned
efficiently. They almost always
smolder for long peroids, creating
unacceptable smoke problems.

Prescribed fire can improve wildlife habitat

In some cases overstory pines are
left during harvest as seed trees, and in
others an unevenaged management
system such as shelterwood is used. In
both situations, the logging debris can
still be burned, but you must take more
care to protect the remaining trees.

Prepare Sites for
Seeding or Planting
Prescribed burning is useful when
regenerating southern pine by direct
seeding, planting, or natural regenera-
tion. On open sites, fire alone can ex-
pose adequate mineral soil and control
competing vegetation until seedlings
become established. Where competing
vegetation cannot be adequately re-
duced by fire, follow up with
mechanical or chemical treatment.
The fire will improve visibility so that
equipment operators can more easily
see the stumps of the harvested trees,
as well as any other hazards. In addi-
tion, if the area is to be bedded before
planting, burning first consumes much
of the debris. The result is more tightly
packed beds and thus better seedling
survival. Where herbicides are used to
kill competition, subsequent burning
will give additional vegetation control.
This step also permits more efficient
and easier movement of hand-planting
crews. Prescribed fire also recycles
nutrients, making them available for
the next timber crop.
For natural regeneration, knowledge
of anticipated seed crop and date of
earliest seed fall is essential. If the

seed crop is inadequate, burning can
be postponed. Complete mineral soil
exposure is not necessary or desirable;
a thin layer of litter should remain to
protect the soil. Generally, burning
should be done several weeks prior to
seed fall. Timing varies with species
and locality.

Improve Wildlife Habitat
Prescribed burning is highly recom-
mended for wildlife habitat manage-
ment where loblolly, shortleaf,
longleaf, or slash pine is the primary
overstory species. Periodic fire tends
to favor understory species that require
a more open habitat. A mosaic of
burned and unburned areas tends to
maximize "edge effect" which pro-
motes a large and varied wildlife
population. Deer, dove, quail, and
turkey are game species that benefit
from prescribed fire. Habitat
preferences of several endangered
species, including the Florida panther,
gopher tortoise, indigo snake, and red-
cockaded woodpecker are also enhanced
by burning. Wildlife benefits from
burning are substantial. For example,
fruit and seed production is stimulated.
Yield and quality increases occur in
herbage, legumes, and browse from
hardwood sprouts. Openings are
created for feeding, travel, and
Selecting the proper size, frequency,
and timing of burs is crucial to the
successful use of fire to improve
wildlife habitat. Prescriptions should

Summer burn for hardwood control

recognize the biological requirements
(such as nesting times) of the preferred
wildlife species. Also consider the
vegetative condition of the stand and,
most importantly, the changes fire will
produce in understory stature and
species composition.

Manage Competing
Low-value, poor-quality, shade-
tolerant hardwoods often occupy or en-
croach upon land best suited to grow-
ing pine. Unwanted species may crowd
out or suppress pine seedlings. In soils
with a high clay content and in areas
with low rainfall during parts of the
growing season, competition for water,
nutrients and growing space may
significantly lower growth rates of the
overstory. Furthermore, understory
trees and shrubs draped with dead
needles and leaves act as ladder fuels
allowing a fire to climb into the
overstory crowns. In most situations,
total eradication of the understory is
neither practical nor desirable.

However, with the judicious use of
prescribed fire, the understory can be
managed to limit competition with
desired species while at the same time
providing browse for wildlife.
Burning is most effective in con-
trolling hardwoods less than 3 inches
in diameter at the ground line. Periodic
fires throughout the rotation can keep
competing vegetation below this 3-inch
threshold. The most desirable season
for burning and the frequency of burns
will vary somewhat by species and
physiographic region. Generally, a
winter (dormant season) fire results in
less root kill than a late spring or sum-
mer burn. One system recommended
in both the Piedmont and Coastal Plain
is a dormant season burn to reduce in-
itial fuel mass, followed by two or
more annual (if enough fuel is present)
or biennial summer burns.
If not controlled, the hardwoods
will form a midstory and capture the
site once the pine is harvested. If a
large pine component is wanted in the
next rotation, these unmerchantable
hardwoods must be removed during
site preparation an expensive

proposition. Generally, fire is required
in combination with other treatments
involving heavy equipment, chemicals,
or both. In many locations the prefer-
red system is a combination summer
burn and herbicide treatment.
However, in the lower Appalachians of
South Carolina, another relatively in-
expensive technique is employed. All
residual hardwoods are felled and the
area broadcast burned under exacting
fuel and weather conditions.

Control Insects And
Brownspot disease is a fungal infec-
tion that may seriously weaken and
eventually kill longleaf pine seedlings.
Diseased seedlings tend to remain in
the grass stage. Control is recom-
mended when more than 20 percent of
the seedlings are infected or when
some of the diseased seedlings are
needed for satisfactory stocking. Once
the seedlings become infected, burning
is the most practical method of disease
control. Any type of burning that kills

Longleaf pine infected with brownspot needle blight

Hardwood topkill after summer burn

...and after prescribed fire

the diseased needles without killing the
terminal bud is satisfactory. Burning
the infected needles reduces the
number of spores available to infect the
seedlings. Generally a fast-moving
winter heading fire under damp condi-
tions, as exist after passage of a strong
cold front, is best. Height growth of
the seedlings often begins the first
postfire growing season.
Reinfection usually occurs quickly
if there are infected seedlings in un-
burned areas near the burned area. If
reinfection occurs, additional burns
may be needed. However, longleaf is
most susceptible to fire immediately
after it comes out of the grass stage.
Therefore, a reburn will likely kill
some seedlings, so such a decision
should be made in consultation with

experienced personnel. Your local
State forestry office is a good place to
Prescribed burning seems to reduce
problems from Fomes annosus root
rot. This fungal disease is less frequent
where periodic burns have reduced the
litter. The fire alters the microenviron-
ment of the forest floor and perhaps
destroys some fruiting bodies and
cauterizes tree stumps.
Prescribed fire has been success-
fully used under very exacting fuel and
weather conditions to control cone in-
sects such as the white pine cone beetle
(Conophthorus coniperda) while the
pest is overwintering in cones on the
ground. Prescribed burning costs
mush less than traditional chemical
control methods used to control th;

Prescribed fire improves range habitat

warm-season grasses promote Dy summer burning

Improve Forage for
Prescribed burning improves
grazing in open pine stands on the
Coastal Plain. Low-intensity burns
increase availability, palatability,
quality, and quantity of grasses and
forbs. Dead material low in nutrient
value is removed while new growth
high in protein, phosphorus, and
calcium becomes readily available.
These benefits are manifested in
increased seasonal cattle weight
gains. Cattle congregate on recently
burned areas so burn location and
size must be carefully selected to pre-
vent overgrazing. One commonly
used system is to divide the range in-
to three parts and burn one third
every year.
A plant may become more or
less abundant after a fire. The
result depends on the stage in the
plant's life cycle at the time of the
fire. Flowering dates vary among
species and with latitude and eleva-
tion within a species' range. There-
fore, observe these dates for the
preferred species, and time the burn
accordingly. For example, wiregrass
responds much better to summer
burns than it does to dormant season

Enhance Appearance
Prescription burning improves
recreation and aesthetic values. For
example, burning maintains open
stands, produces vegetative changes,
and increases numbers and visibility
of flowering annuals and biennials.
Burning also maintains open spaces
such as mountain balds, and creates
vistas. Unburned islands increase
vegetative diversity which attracts a
wider variety of birds and animals. A
practical way to maintain many
visually attractive vegetative com-
munities and perpetuate many en-
dangered plant species is through the
periodic use of prescribed fire.
Using fire to manage landscapes
and enhance scenic values requires
judiciously planned and executed
burns, especially where exposure to
the public is great. Burning tech-
niques can be modified along roads
and in other heavily used areas to en-
sure low flame heights, which in turn
will reduce crown scorch and bark
char while still opening up the stand
and giving an unrestricted view.

Improve Access
Burning underbrush prior to the
sale of forest products improves the
efficiency of cruising, timber mark-
ing, and harvesting. Removing ac-
cumulated material before harvesting
also provides greater safety for
timber markers, loggers and naval
stores operators due to better visi-
bility and less underbrush. The
reduced amount of fuel helps offset
the greater risk of wildfire during
harvesting. Moreover, the improved
visibility and accessibility often in-
crease the stumpage value of the
products. Hikers and other users also
benefit from easier travel and in-
creased visibility. Hunters are more
likely to get a clear shot.

Perpetuate Fire-
dependent Species
Many plants have structural
adaptations, specialized tissues, or
reproductive features that favor them
in a fire-dominated environment.
Such traits suggest a close association
with fire over a very long period of
time. Many endemics are only found
the first 1 to 2 years after a fire.
Changes in the "natural" fire pattern
as a result of attempted fire exclusion
have led to dramatic decreases in
many of these fire-tolerant or fire-
dependent species. Many picturesque
flowers, including several orchids,
currently listed as threatened or en-
dangered are benefited by fire.
Prescribed burning, however, does
not automatically help perpetuate
plant and animal species because
fires are not necessarily conducted
during the same season in which the
site historically burned. The interval
between prescribed fires as well as
fire intensity may also differ from
those of the past. The individual
requirements of a species must
therefore be understood before a fire
can be prescribed to benefit that species.

Prescribed Burning =
Good Wildlife Habitat

Limited access due to fire exclusion



Prescribed burning has direct and Summer Fire W.ner Fire
indirect effects on the environment.
Proper use of prescribed fire, and
evaluation of the benefits and costs of Small Stems Easier To Topkill--
a burn require knowledge of how fire Summer Fire More Effective
affects vegetation, wildlife, soil,
water, and air. Burning techniques
and timing of burns can be varied to so
alter fire effects.
Effects on Vegetation
Fire may injure or kill part of a 70
plant or the entire plant, depending
on how intensely the fire burs and
how long the plant is exposed to high
temperatures. In addition, plant
characteristics such as bark thickness
and stem diameter influence the 60
susceptibility to fire. Small trees of
any species are easier to kill than
large ones.
Southern pine bark has good in-
sulating qualities, and is thicker than
the bark of most hardwood species.
As a result, hardwood trees are
generally much more susceptible to
fire injury than are pines. Pine trees
3 inches or more in ground diameter 40
have bark thick enough to protect the
stems from damage by most prescribed
fires. However, the crowns are quite
vulnerable to temperatures above
135 F. Pine needles will survive ex- 0
posure to 130OF for about 5 minutes,
while similar needles exposed to
1450F for only a few seconds will die.
Very high temperatures are pro-
duced in the flames of burning forest 20
fuels. Fortunately, the hot gases cool
rapidly above the flame zone and are
back to a few degrees above normal
air temperature a short distance from
a prescribed fire unless the wind is o
calm. Adequate wind should be pre-
sent to help dissipate the heat and
slow its rise into the overstory
canopy. Wind is also important in
cooling crowns heated by radiation 0
from fire. Southern pines generally 1 2 3 4 5 6
survive complete crown scorch as D.aH. CLASS (INCHES)
long as there is little needle con-
Hardwood topkill


a Foliage Not Killed Foliage Killed

0 18 30 134 138 142
Temperature (oF)
Lethal time temperature curve

sumption. Severe needle scorch will,
however, retard growth for a year or
more after damage and, in this
weakened state, the trees are more
susceptible to drought and beetle
Temperatures of the air and
vegetation at the time of burning are
critical factors. When the air temper-
ature is 400F, it takes twice as much
heat to kill the foliage in a tree crown
at any given height above a fire than
when it is 900F. The effect of high
air temperature is recognized in using
fire to control understory hardwoods.
Although winter burns will topkill
hardwoods, summer burns are
generally required to kill hardwood
rootstocks. Less heat is needed to
raise plant cells to their lethal
temperature during the summer, and
as a general rule, plants are more
easily damaged by fire when they are
actively growing. In areas with scenic
values, a special effort should be
made to keep needle scorch and bark
char to a minimum.
Even though pine bark is a good
insulator, cambial damage can occur

Differential fire effects

from the extended smoldering of duff
around the root collar. Such damage
is especially likely in previously un-
burned, mature trees where a deep
organic layer has accumulated.
Whenever heat penetrates into the
soil, feeder roots and beneficial soil
organisms are likely to be killed.
Damaged pines are more susceptible
to bark beetle attack, especially if
adverse weather conditions (e.g.
drought) after the burn compound
any loss in tree vigor. However, many
observers report less insect damage
in stands that undergo periodic pre-
scribed burns than in stands where
fire has been excluded.
Prescribed fire generally is not used
in the management of hardwoods in-
tended for harvest once a stand is
established. Fire may not kill large-
diameter hardwoods outright, but it
will often leave fire scars. Such scars
render the lower portion of the bole
unmerchantable and provide entry to
insects and disease.
Many benefits from prescribed
fire, such as reduced hardwood com-

petition, increased forage for grazing,
and improved conditions for wildlife,
depend on changes in the vegetation.
Unwise use of fire may also alter
species composition, but with adverse
results, particularly when relying on
natural regeneration.

Effects on Soil
Specific effects on soil may vary
greatly. Frequency, duration, and in-
tensity of fire, as well as soil character-
istics must be considered. Prescribed
burning in the South normally causes
little or no detectable change in
amount of organic matter in surface
soils. In fact, slight increases have
been reported on some burned areas.
Prescribed underburns will not cause
changes in the structure of mineral
soil because the elevated temperatures
are of brief duration. However, burn-
ing piled or windrowed debris, or
burning when fuel and/or soil moisture
conditions are extremely low, may
elevate temperatures long enough to
ignite organic matter in the soil as
well as alter the structure of soil clays.

Exposing mineral soil in hilly terrain can cause erosion

Leave some duff to protect the soil

As a stand matures, an increasing
proportion of the nutrients on the site
become locked up in the vegetation
and are unavailable for father use un-
til plants die and decompose. Low-
intensity fires speed up this recycling
process, returning nutrients back to
the soil where they are again available
to plants. Under many conditions,
burning may increase nitrogen fixa-
tion in the soil and thus compensate
for nitrogen loss to the atmosphere
that results from burning the litter
layer. When duff layers are not com-
pletely consumed, changes in soil
pore space and infiltration rate are
very slight. If mineral soil is
repeatedly exposed, rain impact may
clog fine pores with soil and carbon
particles, decreasing infiltration rates
and aeration of the soil.
A major concern of the forest
manager is how fires affect surface
runoff and soil erosion. On most
Lower and Middle Coastal Plain
sites, there is little danger of erosion.
In the steeper topography of the Up-
per Coastal Plain and Piedmont,
some soil movement is possible.
However, if the burn is under a
timber stand and some duff remains,
soil movement will be minor on
slopes up to 25 percent. The amount
of soil movement will be greater after
site preparation with heavy machinery
than after prescribed burning.
Care must be taken when clearcut
logging slash is burned on steep
slopes. Until grass and other vegeta-
tion cover the site, surface runoff and
soil erosion may occur. The burning

phase of the "fell and burn" site-
preparation technique commonly used
in the upper Piedmont and mountains
should be completed by mid-September.
This timing allows herbaceous plants
to seed in and provide a winter
ground cover. Burning should not be
done if exposure of highly erosive
soils is likely.
Soil should be wet or damp at the
time of burning to ensure that an
organic layer will remain after a
prescribed burn. Moisture not only
protects the duff layer adjacent to the
soil, but also prevents the fire from
consuming soil humus. If the forest
floor is completely consumed, the
microenvironment of the upper soil
layer will be drastically changed,
making conditions for near-surface
tree roots very inhospitable. Damp
soil also aids mopup after the burn.

Effects on Water
The main effect of prescribed
burning on the water resource is the
potential for increased runoff of rain-
fall. When surface runoff increases
after burning, it may carry suspended
soil particles, dissolved inorganic
nutrients, and other materials into
adjacent streams and lakes reducing
water quality. These effects seldom
occur after Coastal Plain burns. Pro-
blems can be avoided in hilly areas
or near metropolitan water supplies
by using properly planned and con-
ducted burs.
Rainwater leaches minerals out of
the ash and into the soil. In sandy

soils, leaching may also move minerals
through the soil layer into the ground
water. Generally, a properly planned
prescribed burn will not adversely
affect either the quality or quantity of
ground or surface water in the South.

Effects on Air
Prescribed fires may contribute to
changes in air quality. Air quality on
a regional scale is affected only when
many acres are burned on the same
day. Local problems are more fre-
quent and occasionally acute due to
the large quantities of smoke that can
be produced in a given area during a
short period of time.
Smoke consists of small particles
(particulate) of ash, partly consumed
fuel, and liquid droplets. Other com-
bustion products include invisible
gases such as carbon monoxide, car-
bon dioxide, hydrocarbons, and small
quantities of nitrogen oxides. Oxides
of nitrogen are usually produced at
temperatures only reached in piled or
windrowed slash or in very intense
wildfires. In general, prescribed fires
produce inconsequential amounts of
these gases. Except for organic soils
(which are not generally consumed in
prescribed burns), forests fuels con-
tain very little sulfur, so oxides of
sulfur are not a problem either.
Particulates, however, are of
special concern to the prescribed
burner because they reduce visibility.
The amount of particulate put into
the air depends on amount and type
of fuel consumed, fuel moisture con-
tent, and rate of fire spread as deter-

Protect streamside zones

tacKing Tires produce less smoke
than heading fires

mined by timing and type of firing
technique used. Rate of smoke
dispersal depends mainly on atmos-
pheric stability and windspeed.
Effects of smoke can be managed
by burning on days when smoke will
blow away from smoke-sensitive-
areas. Precautions must be taken
when burning near populated areas,
highways, airports, and other smoke-
sensitive areas. Weather and smoke
management forecasts are available as
a guide for windspeed and direction.
Any smoke impact downwind must
be considered before lighting the fire.
The burner may be liable if accidents
occur as a result of the smoke. All
burning should be done in accord-
ance with applicable smoke manage-
ment guidelines and regulations.
During a regional alert when high
pollution potential exists, all pre-
scribed burning should be postponed.
Nighttime burning should be done
with additional care because a tem-
perature inversion may trap the
smoke near the ground. This smoke
can create a serious visibility hazard,
especially in the presence of high
humidities (which occur on most
nights). In particular, smoke mixing
with existing fog will drastically
reduce visibility. Cool air drainage at
night will carry smoke downslope,
causing visibility problems in low-
lands and valleys. On the Coastal
Plain, nighttime air drainage often
follows waterways. Conditions can be
especially hazardous near bridge
crossings because of the higher
humidity there. Of course, the earlier

in the day a fire is completed, the
less likely it is to cause nighttime
smoke problems. More complete
mopup following daytime burning
and nighttime burning only under
very stringent prescriptions can
minimize the occurrence of these
problems. Your local State forestry
office can help with planning night-
time burns.

Effects on Human
Health and Welfare
Occasional brief exposure of the
general public to low concentrations
of drift smoke is more a temporary
inconvenience than a health problem.
High smoke concentrations can,
however, be a very serious matter,
particularly near homes of people
with respiratory illnesses or near
health-care facilities.
Smoke can have negative short-
and long-term health effects. Fire
management personnel who are exposed
to high smoke concentrations often
suffer eye and respiratory system
irritation. Under some circumstances,
continued exposure to high concen-
trations of carbon monoxide at the
combustion zone can result in impaired
alertness and judgement. The proba-
bility of this happening on a prescribed
fire is, however, virtually nonexistent.
Over 90 percent of the particulate
emissions from prescribed fire are
small enough to enter the human
respiratory system. These particulates
can contain hundreds of chemical
compounds, some of which are toxic.

The repeated, lengthy exposure to
relatively low smoke concentrations
over many years can contribute to
respiratory problems and cancer. But,
the risk of developing cancer from
exposure to prescribed fire has been
estimated to be less than 1 in a
Although the use of herbicides in
forest management has increased all
chemicals are now tested before being
approved for use, and we are more
careful than ever to minimize their
potential danger. Many of them break
down rapidly after being applied.
Moreover, both theoretical calcula-
tions and field studies suggest that
prescribed fires are hot enough to
destroy any chemical residues.
Minute quantities that may end up in
smoke are well within currently-
accepted air quality standards.
Threshold limit values (TLV's) are
often used to measure the safety of
herbicide residues in smoke. Ex-
pected exposure rates of workers to
various brown-and-burn combinations
have been compared with TLV's.
They showed virtually no potential
for harm to workers or the general
There is at least one group of
compounds carried in smoke that can
have an immediate acute impact on
individuals. When noxious plants
such as poison ivy burn, the smoke
can cause skin rashes. These rashes
can be much more widespread on the
body than those caused by direct con-
tact with the plants. If you breathe
this smoke, your respiratory system
can also be affected.

Effects on Wildlife
The major effects on wildlife are
indirect and pertain to changes in
food and cover. Prescribed fires can
increase the edge effect and amount
of browse material, thereby improv-
ing conditions for deer and other
wildlife. Quail and turkey favor food
species and semi-open or open condi-
tions that can be created and main-
tained by burning. Burning can im-
prdve habitat for marshland birds and
animals by increasing food produc-
tion and availability.
The deleterious effects of prescribed
fire on wildlife can include destruction
of nesting sites and possible killing of
birds, reptiles, or mammals trapped
in the fire. Fortunately, prescribed
fires can be planned for times when

Smoke sensitive areas can be impacted by prescribed fire

nests are not being used. Also,
virtually all the types of prescribed
fire used in the South provide ample
escape routes for wildlife. For example,
a large tract was operationally burned
with aerially-ignited spot fires and
immediately examined for wildlife
mortality. Fish and game agency
personnel found none, but noted deer
moving back into the still-smoking
burn. The ill-advised practice of
lighting all sides of a burn area (ring
firing) is a primary cause of animal
entrapment and has no place in under-
burning. It also results in unnecessary
tree damage as the flame fronts merge
in the interior of the area.
Management of the endangered red-
cockaded woodpecker presents a
special problem because of the
copious amounts of dried resin that
stretch from the nest cavity toward
the ground. The bird requires habitat
historically maintained by fire, even
though these pitch flows can be
ignited, carrying fire up to the cavity.
This is unlikely, however, if short
flame lengths are prescribed. Fuel
can also be raked from around cavity
trees as an added precaution.
Prescribed fire does not benefit
fish habitat, but it can have adverse
effects. Riparian zone (streamside)
vegetation must be excluded from
prescribed burns to protect high
quality plant and animal habitat, and
water quality. When shade is removed,
water temperatures will increase.
Burning conditions are often un-
favorable along streams because of
increasing fuel moisture, making line
plowing optional. But a buffer zone
should always be left. If in doubt, a
control line should be put in.

Effects on Aesthetics
The principal effect of prescribed
burning on aesthetics can be sum-
marized in one word: contrast. Con-
trast, or change from the preburn
landscape, may be positive or negative
depending largely on personal opinion.
What may be judged an improvement
in scenic beauty by one may be con-
sidered undesirable by another.
Many of the undesirable impacts
are relatively short term and can be
minimized by considering scenic
qualities when planning a burn. For
example, the increased turbulence
and updrafts along roads and other
forest openings will cause more in-
tense fire with resulting higher tree
trunk char and needle scorch.

Prescribed burning attracts wildlife

Generally, the more immediate un-
favorable impacts such as smoke and
ash, topkilled understory plants, and
a blackened forest floor are necessary
to achieve two major benefits -
increased visual variety and increased
visual penetration.
Variety or diversity in vegetative
cover will create a more pleasing,
general visual character to the stand.
Similarly, scenic qualities of the forest
can be better appreciated if the stand
can be made more transparent. An
example is the reduction of an under-
story buildup along a forest road that
will permit the traveler to see into the
interior of the stand, perhaps to a
landscape feature such as a pond or

interesting rock outcrop. The smutty
appearance of the ground will "green
up" fairly quickly. Any scorched needles
will soon drop and not be noticeable.
Flowers and wildlife will increase.
Some important points are: 1) The
apparent size of a burn can be reduced
by leaving unburned islands to create
a mosaic pattern of burned and un-
burned area. 2) Where hardwood in-
clusions are retained, make sure they
are large enough to be relevant to the
observer. 3) Observer criteria must be
understood if reactions to a burn are
to be' predicted. Personal reactions
will depend on observer distance,
duration or viewing time, and aspect.

AesinelCa can ve ennancea Dy prescruea inre

Weather and Fuel


Important Weather
A general understanding of the
separate and combined effects of
several weather elements on the
behavior of fire is needed if you are
to plan and execute a good burn.
Wind, relative humidity, temperature,
rainfall, and airmass stability are the
more important elements to consider.
These factors influence fuel moisture
which is critical to success. Because
weather and fuel factors interact, an
experienced prescribed burner can
conduct a successful burn even with
one or more factors slightly outside
the desired range as long as they are
offset by other factors. You should
become familiar with local weather
patterns that are favorable for
prescribed burning as well as local
"watchout" situations.
Good winter prescribed burning
conditions often exist for several days
after the passage of a cold front that
has brought 1/4 to 3/4 inch of rain.
During this time, persistent winds, Anamometer Precipitation gauge
low relative humidities, cool tempera-
tures and sunny days can be
anticipated. Weather conditions for
summer burning are much less
Before starting to burn, obtain the
latest weather forecast for the day of
the burn and the following night. A.
When possible, get a 2-day weather
outlook. Knowledge of weather is
the key to successful prescribed
burning, and is mandatory for
II proper management of smoke
produced by burning.

Fire-weather shelter

Knowledge of weather is essential for a successful burn

Successful DacKing tires need steady winds

Sources of Weather
Ordinarily, four sources of
weather information are available.
Use one or more of them before and
during prescription fires. The sources
Local National Weather Service
offices will furnish weather forecasts
and outlooks via radio and television.
Spot weather forecasts are also
-available, but their value depends
upon the forecaster's knowledge of
local conditions. Inexpensive radios
are also available that continually
monitor National Oceanic and At-
mospheric Administration (NOAA)
weather-related information and
forecast updates. Do not rely solely
on the NOAA broadcasts because this
information is not specific enough for
smoke-management planning.
The best source of information in-
cluding current forecasts and outlooks
is generally the local office of your
State forestry agency. The person you
talk to can often help you interpret
the forecast, give you any warnings,
and pass on pertinent information
such as other burs planned for that
day, The prescribed burner should
take full advantage of such services.
All southern State forestry agen-
cies and national forests, as well as
many military bases and private con-
cerns operate fire-danger stations.
The basic weather parameters
measured at these sites are very
useful. However, National Fire


Danger Rating System (NFDRS)
indices which are calculated from
these measurements should not be
used. This system was designed to
provide a worst-case scenario for
wildfire control over very large areas.
It was not designed as a planning tool
for prescribed burning!
Weather observations should be
made at the prescribed burn site
immediately before, during and im-
mediately after a fire. Such observa-
tions are important because they
serve as a check on the applicability
of the forecast and keep the burning
crew up-to-date on any local in-
fluences or changes. Take readings in
a similar area upwind of the fire to
avoid heating and drying effects of
the fire. Do this at 1- to 2- hour inter-
vals, or more often if changes in fire
behavior are noticed. Measurements
taken in an open area, on a forest
road, and in a stand are likely to dif-
fer widely. Easy-to-use belt weather
kits that include a psychrometer and
an anemometer are available. By
using this kit and observing cloud
conditions, a competent observer can
obtain a fairly complete picture of the
current weather.

Prescribed fires behave in a more
predictable manner when windspeed
and direction are steady. Onsite
winds vary with stand density and
crown height. Windspeed generally
increases to a maximum in the early
afternoon and then decreases to a
minimum after sunset. The preferred
range in windspeed in the stand is 1
to 3 mph (measured at eye-level) for
most fuel and topographic situations.

Windspeed readings for most fire-
weather forecasts are, however, taken
20 feet above ground at open loca-
tions. Windspeeds in fire-weather
forecasts are the maximum expected
and not the average for the day. The
minimum 20-foot windspeed for burning
is about 6 mph and the maximum is
about 20 mph. These are the most
desirable winds for prescribed burning,
but specific conditions may tolerate
other speeds. As a general rule
higher windspeeds are steadier in
Relatively high winds quickly
dissipate the heat of a backing fire.
The result is less crown scorch than
from a fire backing into a low-speed
wind. In-stand windspeeds should be
in the low to middle range (1 to 2
mph) when heading fires are used.
With high winds, heading fires
spread too rapidly and become too
intense. On the other hand, enough
wind must be present to keep the
heat from rising directly into tree
crowns. Mature southern pine stands
with a sparse understory can be
burned at very low windspeeds -
just enough to give direction to the
Of greater importance than wind-
speed is the length of time the wind
blows from one direction. Presistent
wind directions occur frequently dur-
ing winter, especially following
passage of a cold front when winds
are typically from the west or
northwest. As these winds slowly
shift clockwise over the next few
days, they become weaker and less
steady. Winds with an easterly com-
ponent are generally considered
undesirable for prescribed burning.
However, along the coast, sea and
land breezes are often utilized. Ir-

respective of direction, a forecast of
wind steadiness should always be ob-
tained. For sites near the coast, also
obtain the expected time of sea
breeze arrival and departure.
The most critical areas, with
regard to fuel and topography, should
be burned when wind direction is
steady and persistent. Relatively easy
burns can be conducted under less
desirable wind conditions. Topography,
and local effects such as stand open-
ings, roads, etc. may have a bearing
on favorable wind conditions and
should always be considered when
planning a burn.

1 MPH to 3 MPH

Debris Burning
Winds are stronger in open areas
than they are in the forest. Because
there is no overstory to protect, wind
is not needed to cool the heated com-
bustion products. However, from a
smoke management standpoint, the
stronger the wind the better the
dispersion-provided there are no
downwind smoke-sensitive areas that
will be impacted. When broadcast
burning, eye-level winds over 3 to 4
mph can create containment problems
if a heading fire is used. With piled
or windrowed debris, eye-level winds
of 8-10 mph can be tolerated by ad-
justing the firing pattern.
Wind direction may change
substantially with height, but it is
these transport winds that regulate

the movement of the smoke column.
Moderate transport windspeeds allow
a convection column to develop that
exhausts the smoke high into the
atmosphere where it quickly disperses
with a minimum impact on ground-
level air quality. Before setting a fire
that will generate a convection col-
umn, however, obtain information on
the existing and forecast wind pro-
files. If an adverse profile exists, it is
likely to result in an unacceptably
high spotting potential. Fire behavior
characteristics are associated with
various wind profiles. They are
described in Byram's publication,
listed in the Suggested Reading
section. Once the fire has died down
and smoke production is from
smoldering combustion, surface wind
is necessary to ensure good smoke

Relative Humidity
Relative humidity is an expression
of the amount of moisture in the air
compared to the total amount the air
is capable of holding at that temperature
and pressure. Each 200 rise in temp-
erature (which often occurs during
the morning hours on a clear day)
reduces the relative humidity by
about half, and likewise, each 200
drop in temperature (which often oc-
curs in early evening) causes relative
humidity to roughly double. When a
cold front passes over an area, the air
behind the front is cooler and drier
than the old airmass it is replacing.
The result is a drop in both

temperature and humidity.
Preferred relative humidity for
prescribed burning varies from 30 to
55 percent. Under special conditions,
a wider range of relative humidities,
as low as 20 percent and as high as
60 percent, can produce successful
burns. When relative humidity falls
below 30 percent, prescribed burning
becomes dangerous. Fires are more
intense under these conditions and
spotting is much more likely; pro-
ceed only with additional precau-
tions. When the relative humidity is
60 percent or higher, a fire may leave
unburned islands or may not burn hot
enough to accomplish the desired
The moisture content of fine, dead
fuel such as pine needles and dried
grasses responds rapidly to changes
in relative humidity. However, there
is a timelag involved for fuels to
achieve equilibrium with the moisture
condition of the surrounding at-
mosphere. Also, previous drying and
wetting will influence fuel moisture.
Therefore, the relative humidity and
fuel moisture must be assessed


Debris Burning
Relative humidity (along with
temperature) controls fuel moisture
content up to about 32 percent.
Liquid moisture such as rain or dew


\ Relative Humidity
Daily temperature/
relative humidity cycle 1

must contact a fuel for moisture con-
tent to rise above 32 percent, and the
increase depends upon duration as
well as the amount of precipitation.
Recently-cut pine tops have a dry-
ing rate that is somewhat independent
of relative humidity as long as the
mositure content of fresh tops
(needles still green) is above about 32
percent. Once this material initially
dries to a moisture content below 32
percent, it behaves as a dead fuel and
becomes much more responsive to
daily fluctuations in relative humidity.
The response to changes in relative
humidity is much more rapid in fine
dead fuels suspended above the
ground than in those that have
become part of the litter layer. These
elevated needles and other suspended
dead materials are not in contact with
the damp lower litter and are more
exposed to the sun and wind.
When burning piled debris, once
the larger-diameter fuels ignite, in-
creases in relative humidity have little
effect on fire behavior during the ac-
tive burning phase. Low humidities
(below 30 percent), however, will
promote spotting and increase the
likelihood of fire spreading between

The average instantaneous lethal
temperature for living tissue is about
1450F. Air temperatures below 60F
are recommended for winter under-
burs because more heat is needed to
raise foliage or stem tissue to lethal
temperature levels. When the objec-
tive is to control undesirable species,
growing-season burns with ambient
air temperatures above 800F are
recommended. These conditions in-
crease the likelihood of reaching kill-
ing temperatures in understory stems
and crowns. Of course, the overstory
pines must be large enough to escape
injury. Larger trees have thicker bark
and their foliage is higher above the
flames, which allows more room for
the hot gases to cool before reaching
the crowns.
Temperature strongly affects
moisture changes in forest fuels.
High temperatures help dry fuels
quickly. When fuels are exposed to
direct solar radiation, they become
much warmer than the surrounding
air. Moisture will move from the
warmer fuel to the air even though
the relative humidity of the air is

high. Temperatures below freezing,
on the other hand retard fire intensity
because additional heat is required to
convert ice to liquid water before it
can be vaporized and driven off as
steam. Consequently, it does not take
much moisture under these conditions
to produce a slow-moving fire that
will leave unacceptably large areas


Debris Burning
Cleared areas are often burned
when ambient air temperatures are
high. There is no overstory present to
worry about and surface heating from
direct sunlight usually increases the
mixing height which helps disperse
the smoke.
It is particularly important to use
an ignition pattern such as center
firing when ambient air temperatures
are high. This tactic draws the heat
into the cleared area and prevents
heat damage to trees in adjacent
Rainfall and Soil
Because rainfall affects both fuel
moisture and soil moisture, you
should have some idea of the amount
of rain falling on the area to be
burned. In winter, rainfall is fairly
easy to forecast throughout the South.
In summer, when shower activity
prevails, predicting rainfall at in-
dividual locations is much more
difficult. The only reliable method to
determine the amount of precipitation
that actually falls is to place an
inexpensive rain gauge on the site.
The importance of adequate soil
moisture can't be overemphasized.
Damp soil protects tree roots and
microorganisms. Even when burning
to expose a mineral soil seedbed it is
desirable to leave a thin layer of
organic material to protect the soil
surface. Burning should cease during
periods of prolonged drought and
resume only after a soaking rain of
at least 1 inch. As soil moisture con-
ditions improve, less rain is needed
before burning. If recent precipitation
has been near average, 1/4 to 1/2 inch
of rain followed by sunny skies, brisk

winds, and low humidities will
generally result in several days of
good prescribed fire conditions with
adequate soil protection.
On clay soils, such as are found in
the Piedmont, much of the rainfall is
lost through surface runoff, and dura-
tion is more important than amount.
For example, 1 inch of rain occurring
in 1/2 hour will not produce as large
a moisture gain as 1/2 inch falling
over a 2 hour period.


Debris Burning
Generally, rain has a much greater
effect on fuel moisture in cleared
areas than under a stand because
none is intercepted by tree canopies.
However, fuels also dry much faster
in cleared areas because of increased
sunlight and higher windspeeds. This
differential drying can often be used
to advantage from a fire-control
standpoint. Burn the cleared area
several days after a hard rain while
fuels in the surrounding forest are
still damp. Burning under these con-
ditions assures good soil moisture.
However, when burning cleared
areas, soil damage is as much a func-
tion of fire intensity and duration as
it is of soil moisture. Intense, long-
duration fires will bake the soil
regardless of the moisture present.
Both the chemical and physical prop-
erties of the soil can be altered. This
type of fire should be avoided,
especially on clay soils and steep
slopes. These undesirable fire effects
are often produced when burning
windrowed or piled debris, and are
one reason piling or windrowing
slash prior to burning are

Fine-fuel Moisture
Fine-fuel moisture is strongly in-
fluenced by rainfall, relative humidity,
and temperature. The preferred range
in actual (not calculated) fine-fuel
moisture of the upper litter layer (the
surface layer of freshly fallen needles
and leaves) is from 10 to 20 percent.
Burning when fine-fuel moisture is
below 6 or 7 percent can result in
damage to plant roots and even the
soil. When fine-fuel moisture ap-

20 30 40
Relative Humidity (percent)

Fuel-moisture sticks

Effects of humidity and days since rain on fine-fuel

preaches 30 percent, fires tend to
burn slowly and irregularly, often
resulting in incomplete burns that do
not meet the desired objectives.
However, when areas with very heavy
fuel buildups or extensive draped
fuels are burned, moisture content
should be 20 to 25 percent to keep
fire intensity manageable, especially
if aerial ignition techniques are used.
Fine-fuel moisture values obtained
from NFDRS tables on fire-behavior
models are considerably less than
these actual values.
Some experienced practitioners
can accurately estimate fuel moisture
by examining a handful of litter.
However, the only sure way to tell is
to take a sample and ovendry it.
Tables and equations in the National
Fire Danger Rating System and
BEHAVE can be used to estimate
fine-fuel moisture, but the results are
invariably underestimates (because
they are worst-case values designed
for use in predicting wildfire
behavior). One simple test that will
give a very rough estimate of the
upper-litter-layer moisture content is
to pick up a few pine needles and in-
dividually bend each in a loop. If the
needles snap when the width of the
closing loop is about 1/4 to 1/2 inch,
their moisture content is between 15
and 20 percent. If they do not snap
in two, they are too wet to burn well.
If they crumble into small pieces they
are exceedingly dry and even if the
lower litter is moist, the fire may
cause damage and be difficult to con-
trol. Fuel moisture sticks that respond
to weather changes like 10-hour fuels
are available. With a good set of
scales and proper placement of the
sticks, acceptable fuel moisture

estimates can be obtained just before
ignition. These values will differ
slightly from actual fine-fuel
moistures, but are fairly represen-
tative of most southern fuel types.
They are much closer to actual fine-
fuel moistures than are calculated or
tabular values.
Lower litter should always be
checked before burning to make sure
it feels damp. This will help ensure
that some remains, even though char-
red, to leave a protective covering
over the soil. Generally, the moisture
content increases from the litter sur-
face down through the duff layer to
the soil. Exceptions can occur after a
light shower, or in the morning after
a heavy dew. In these cases, fires
often burn more intensely than would
be expected from just looking at the
upper-litter-layer moisture content.
When burning on organic soils this
phenomenon can have drastic conse-
quences. If the fire dries the moist
surface layer of peat, the organic soil
will ignite. These fires can impact an
area for many weeks in spite of con-
trol efforts, causing extensive smoke
The speed with which fine fuels
respond to changes in humidity
depends on fuelbed characteristics
such as whether the fuelbed consists
of compacted hardwood leaves or
jack-strawed pine needles. Different
fuel types can reach different moisture
contents under the same humidity
conditions. For example, grassy
openings containing cured material
can be burned within hours of a
drenching rain if good drying condi-
tions exist. Because of these natural
variations, recommended fine-fuel
moisture values are only guidelines.

On-the-ground knowledge of fuels
must be incorporated into the
Fuel moisture also influences
smoke production. When very damp
woody fuels burn, large amounts of
characteristic white smoke are given
off. Much of the visible smoke plume
is actually condensed water vapor.


Debris Burning
Harvested areas should be burned
when fuels are dry. They will ignite
easier, burn more quickly and com-
pletely, shortening the time necessary
to complete the burn. Less mopup
will be required and the impact on
air quality will be reduced. The short
but severe summer droughts common
throughout much of the South pro-
vide ideal burning conditions on
cleared areas, provided soil moisture
does not get too low.
To avoid the possibility of un-
necessary damage to the site, debris
should be burned as it lies (broadcast
burned) rather than piled. Because
fuels on logged areas receive full
solar radiation, they dry before sur-
rounding forest fuels do. It takes at
least several weeks after cutting for
the severed tree tops to cure. Once
the needles turn a greenish-yellow

Prescribed Burned Forests
are More Productive

and the hardwood leaves wither, the
debris is ready to burn. Cleared areas
can then be safely burned soon after
a rain, before adjacent forest fuels
dry enough to burn well. Ten-hour
fuel moisture (fuels 1/4 to 1 inch in
diameter, such as branches and small
stems) is a better indicator of burning
conditions in slash fuels than is fine-
fuel moisture. Fuel moisture sticks
will give excellent results. One set of
"sticks" can be placed on the area to
be burned and another in the nearby
undisturbed forest. Let the sticks
become acclimated for at least 2
weeks before reading. Many
managers consider the area ready to
burn when the moisture content of
the sticks on the logged area reaches
about 10 percent while that of those
in the forest is still above 15 percent.
If the burn objective is to consume
larger fuels (over 2 to 3 inches in
diameter), piling will probably be
necessary. Piling in wet weather
should be avoided. Keep the piles
small and free of dirt. Allow fresh
logging debris to cure for several
weeks before piling because drying
conditions are exceedingly poor in
the middle of a pile, especially if it is
compacted or contains much dirt.
Much of the smoke problem associated
with burning piled debris is caused
by inefficient combustion of damp,
soil-laden piles. These piles may
smolder for days or weeks.

Airmass Stability and
Atmospheric Dispersion
Atmospheric stability is the
resistance of the atmosphere to vertical
motion. When the atmosphere is
stable, temperature decreases slowly
as altitude increases (less than 5.5 0F
per 1,000 feet). Under very stable
conditions, inversions may develop in
which temperature actually increases
with height. The distance from the
ground to the base of this inversion
layer is called the mixing height.
Under less stable atmospheric condi-
tions, other factors beyond the scope
of this discussion determine the
height of the mixing layer. In either
case, the mixing layer is defined as
the layer of air within which vigorous
mixing of smoke and other pollutants
takes place. The average windspeed
throughout the mixing layer is called
the transport windspeed. Mixing
heights above 1,700 feet and transport

windspeeds above 9 mph are
desirable for good smoke dispersion.
Some prescribed burners on the
Ozark Plateau believe their fires
become difficult to control when the
mixing height is greater than 6,500
The old adage that hot air rises is
true but only as long as it is warmer
than the surrounding air. Thus, stable
air tends to restrict convection col-
umn development and produces more
uniform burning conditions.
However, combustion products are
held in the lower layer of the at-
mosphere (especially under
temperature inversions). Visibility is
likely to be reduced because of
smoke accumulation. As the earth
cools each night, the air near the
ground is cooled more than the air
above, forming a stable layer.
Because this cold air is denser, it
drains into low-lying areas such as
swamps and bottomlands, carrying
with it smoke from smoldering
stumps, branches and other debris.
When the atmosphere is unstable,
the decrease in temperature with
height exceeds 5.5 F per 1,000 feet.
Once a parcel of air starts to rise, it
will continue to rise until it cools to
the temperature of the surrounding
air. Such conditions promote convec-
tion and rapid smoke dispersion but,
if severe, can make fire control
A neutral atmosphere is one in
which a rising parcel of air remains
at the same temperature as its sur-
rounding environment (i.e., the
temperature decrease with altitude
equals the dry adiabatic lapse rate of
5.5F per 1,000 feet). Smoke disper-
sion in a neutral atmosphere can be
adequate if windspeed is sufficiently
high. But remember, you need to ac-
count for the effect of the wind on
fire control.
Obtain forecasts of mixing height,
transport windspeed, and atmospheric
stability, but also observe local in-
dicators at the fire site. Indicators of
a stable atmosphere are steady winds,
clouds in layers, and poor visibility
due to haze and smoke hanging near
the ground. Unstable conditions are
indicated by dust devils, gusty winds,
clouds with vertical growth, and
good visibility.
A prescribed fire generates vertical
motion by heating the air. If the at-
mosphere is unstable, the hot com-
bustion products will rise rapidly

because of the large temperature dif-
ference between the smoke and sur-
rounding air. The column will con-
tinue to build in height as long as it
remains relatively stationary and is
heated by new combustion products
faster than it is being cooled. The
stronger the convective activity, the
stronger the indrafts into the fire.
This effect increases fire intensity by
producing even stronger convective
activity. Eventually spotting, crown-
ing and other indicators of erractic
fire behavior develop. Supress such a
fire as quickly as possible to hold
damage to a minimum. With adequate
planning, this situation rarely develops
when underburning, using conven-
tional ground-ignition techniques.
However, when using aerial ignition
techniques at the high end of the
prescription window, you can ignite
too much area too quickly. This ac-
tion results in severe damage to the
overstory. The behavior of the first
row or two of spots should warn the
burning boss to halt ignition and
observe fire behavior before making a
decision to adjust the ignition pattern,
change firing techniques, or terminate
the burn.


1,700 TO 6,500 FEET ABOVE

9 TO 20 MPH

Debris Burning
Strong convection over cleared
areas burned for site preparation or
slash disposal helps vent smoke into
the upper atmosphere. A convection
column will continue to rise until it
cools to the temperature of the sur-
rounding air or until it reaches the
base of an inversion layer. A well-
developed convection column produces
strong indrafts which help confine
this type fire to its prescribed area.
Care must be taken to ensure that all

burning materials sucked into the
convection column burnout before be-
ing blown downwind and dropping to
the ground to act as firebrands.
Whenever a burn site is in hilly
terrain, diurnal slope winds must be
considered. As soon as a slope is
heated by the morning sun, an
upslope breeze results. This breeze
will increase to a maximum (< 8 mph)
during the early afternoon and end as
the slope cools in the evening. As the
slope continues to cool, a downslope
wind will develop, reaching a max-
imum (<5 mph) after midnight. This
breeze will end after sunup as the
slope again begins its daily heating
cycle. If you ignite a fire at the base
of a slope during the day, differential
heating will be greatly increased. The
fire will rapidly spread uphill, giving
the combustion products added lift to
help vent them into the atmosphere.
However the nighttime downslope
wind will have the opposite effect,
concentrating any drift smoke in
low areas.

Weather is the Vital Element of
Prescribed Burning -- Use the
Weather Forecasts

High fuel moistures produce lots of smoKe

Unstable conditions and/or a high mixing height provide for rapid smoke

Firing Techniques

Various firing techniques can be
used to accomplish a burn objective.
The technique chosen must be corre-
lated closely with burning objectives,
fuels, topography, and weather factors
to prevent damage to forest resources.
The proper technique to use can change
as these factors change. Atmospheric
conditions should be favorable for
smoke to rise into the upper air and
away from smoke-sensitive areas such
as highways, airports, and urban areas.
Based on behavior and spread, fires
either move with the wind (heading
fire), against the wind (backing fire),
or at right angles to the wind (flank-
ing fire). The movement of any fire
can be described by these terms. For
example, a spot fire would exhibit all
three types. Heading fire is the most
intense because of its faster spread
rate, wider flaming zone, and longer
flames. Backing fire is the least in-
tense, having a slow spread rate
regardless of windspeed. This type of
fire has a narrow flaming zone, and
short flames. Flanking fire intensity
is intermediate. The slope of the land
has an effect on rate of spread similar
to that of wind.
If you encounter slight variations
in fuel volumes or weather condi-
tions, consider combining two or
more firing techniques to achieve the
desired result. A solid line of fire
always spreads faster and thus builds
up intensity quicker than does a
series of spot ignitions spaced along
the same line. Intensity increases
abruptly when two fires burn
together. The magnitude of this in-
crease is greater when fires converge
along a line rather than along a mov-
ing point. The line of crown scorch
often seen paralleling a downwind
control line delineates the zone where
a heading fire and a backing fire
Residence time is the time it takes
the flaming zone to move past a
given point. The residence time of
heading and backing prescribed fires
is often about the same because the
deeper flame depth of a heading fire

compensates for its faster movement.
Generally, backing fires consume
more forest floor fuels than do
heading fires. The total heat applied
to a site may be roughly equal for
both heading and backing fires, as
long as additional fuels are not in-
volved. This result can be expected
even though the fireline intensity of

the heading fire would be greater. In
a backing fire, the released heat
energy is concentrated closer to the

Using a driptorch

Heading fire may be used with light fuel loadings

Flaming Zone
Flame Depth

Flame dimensions for a wind-driven fire

Buffer Strip

RPloo _ne

Reproduction .sne

Backing fire technique

Cultivated Field Fire


Backing Fire
A backing fire is started' along a
baseline (anchor point), such as a
road, plow line, stream or other barrier,
and allowed to back into the wind.
Variations in windspeed have little
effect on the rate of spread of a fire
burning into the wind. Such fires
proceed at a speed of 1 to 3
chains per hour. Backing fire is the
easiest and safest type of prescribed
fire to use, provided windspeed and
direction are steady. It produces
minimum scorch and lends itself to
use in heavy fuels and young pine
Major disadvantages are the slow
progress of the fire and the increased
potential for feeder-root damage with
increased exposure to heat if the lower
litter is not moist enough. When a
large area is to be burned, it often
must be divided into smaller blocks
with interior plow lines (usually
every 5 to 15 chains). All blocks
must be ignited at about the same
time to complete the burn in a timely
manner. In-stand winds of 1 to 3 mph
at eye level are desirable with back-
ing fires. These conditions dissipate
the smoke and prevent heat from ris-
ing directly into tree crowns.
When the relative humidity is low,
a steady wind is blowing, and fuels
are continuous, an excellent burn can
be anticipated once the fire backs
away from the downwind control line.
Under such conditions, however, extra
care must be taken to make sure the
initial fire doesn't spot across the line.

Factors Associated with Backing
Must be ignited along the down-
wind control line.
Use in heavy roughs.
Use in young stands (minimum
basal diameter of 3 inches) when air
temperature is below 45F.
Normally result in little scorch.
Costs are relatively high because
of additional interior plow lines and
extended burning period resulting
from slower movement of the fire.
Not flexible to changes in wind
direction once interior lines are
Requires steady in-stand winds
(optimum: 1 to 3 mph).
Will not burn well if actual fine-
fuel moisture is above 20 percent.
Requires good fuel continuity to
carry well.
A single torch person can pro-
gressively ignite lines. 2

Strip-Heading Fire
In strip-headfiring, a series of
lines of fire are set progressively up-
wind of a firebreak in such a manner
that no individual line of fire can
develop to a high energy level before
it reaches either a firebreak or
another line of fire. A backing fire is
generally used to secure the base line
and the remainder of the area then
treated with strip-heading fires. Strips
are often set 1 to 3 chains apart. The
distance between ignition lines is
determined by the desired flame
length. This distance can be varied
within a fire to adjust for slight
changes in topography, stand density,
weather, or the type, amount or
distribution of fuel. Compensation
for minor wind direction changes can
be made by altering the angle of strip
fire with the base line. Treat major
changes in fuel type separately. An
effective method of reducing fire in-
tensity is to use a series of spots or
short 1- to 2-foot-long strips instead
of a solid line of fire. An added ad-
vantage of these short strips or spots
is that driptorches will not have to
be filled as often. Strip-heading fires
permit quick ignition and burnout,
and provide for smoke dispersal
under optimum conditions. However,
higher intensities will occur wherever
lines of fire burn together, increasing
the likelihood of crown scorch.
Occasionally, on areas with light
and even fuel distribution, a heading
fire may be allowed to move over the
entire area without stripping to better
accomplish the objectivess. This
method reduces the number of areas
of increased fire intensity that occur
each time two fires burn together.
Caution: Be sure the fire will not
escape control. First set a backing
fire along the downwind control line
and allow it to burn out.a strip wide
enough to control the heading fire.

Factors Associated with Strip-
heading Fires
* Secure the downwind base line
before igniting a heading fire.
* Do not use in heavy roughs. Con-
sider alternative techniques if fire-
free interval exceeds 3 years.
* Winter use is best because cool
weather (below 60"F) helps avoid
crown scorch.
* Use in medium-to-large
sawtimber. May be used for annual
plantation maintenance burns after in-
itial fuel reduction has been
* Can be used in "flat" fuels such as
hardwood leaves.
* Is a good method for brownspot
* Because fire movement is fast,
large blocks can be burned.
* Can be used with high relative
humidity (50 to 60 percent) and high
actual fine-fuel moisture (20 to 25



Burned Out I

* Needs just enough wind to give
direction (1 to 2 mph in-stand).
* Cost is lower than other line-
firing techniques because fire pro-
gress is rapid and few plow lines are
* The technique can accommodate
wind shifts up to about 45 degrees.
* Flame lengths increase whenever
heading fire converges with a backing
fire, thereby increasing the possibility
of crown scorch.
* A single torch person can pro-
gressively ignite strips.
* Do not force a burn on a marginal
day at the low end of the prescription
window. The fire may burn slowly
until after the crew leaves, then pick
up intensity and escape.

S\ Plow Line



Strip-heading fire technique

Flanking Fire
The flanking-fire technique con-
sists of treating an area with lines of
fire set directly into the wind. The
lines spread at right angles to the
wind. This technique requires con-
siderable knowledge of fire behavior,
particularly if used by itself. It is
used quite often to secure the flanks
of a strip-heading fire or backing fire
as it progresses. It is sometimes used
to supplement a backing fire in areas
of light fuel or under more humid
weather conditions. It is useful on a
small area or to facilitate burning a
large area in a relatively short time
when a line-heading fire would be
too intense.

Buffer Strip WIN

Plow Line


This method of firing can stand
little variation in wind direction and
requires expert crew coordination and
timing. For safety, all lines of flank
fire should be ignited simultaneously
and all torch people should keep
abreast of one another. If only one or
two torch people are available, this
technique is usually altered to set the
ignition lines 45 degrees into the wind.
In the Piedmont, any ignition line
that drops perpendicularly off a ridge
creates a flanking fire under no-wind
conditions. If several lines are ignited
off the end of a ridge or knoll, the
pattern looks like a chevron or maple



Control Line

Factors Associated with Flanking
* Always secure downwind base line
* Fuel loading should be light to
medium-less than 8 tons per acre.
0 Wind direction must be steady.
0 Best used in medium-to-large
0 Allows fast area ignition.
0 Needs few control lines.
0 In areas with a high understory,
multiple torch people are needed and
coordination is very important. Use
radio communications whenever torch
people cannot see one another.
* Useful in securing flanks of other
fire types.

Flanking fire technique

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distance between lines, firing should
be halted. Allow the area to burn
with a backing fire or plow it out.
Although intensity at the head of an
individual spot is increased by widen-
ing the distance between lines, the
average intensity of the bur as a
whole is usually somewhat lower.
Check to see that convergence-zone
flame lengths are within tolerable
limits, and that other fire behavior
parameters appear satisfactory. If
everything is within prescription, you
can increase both between- and
within-line distances. This step will
reduce ignition time, and decrease
the number of ignitors used. The
number of convergence areas with
their higher intensities will also be
Experience to date shows grids up
to 4 chains by 4 chains (one ignition
point every 1.6 acres) can produce
excellent results. The time needed to
complete the burn can be reduced by
offsetting successive ignition lines by
one half of the within-line spacing.
The heading fires from one line will
then come up between the backing
fires on the next line.

Factors Associated with Point
Source Fires
Assume much of the area will be
burned by heading and flanking fires
and very little by backing fires.
If conditions are ideal for tradi-
tional line-backing fires, point source
fires may be too intense.
Preferred burning conditions in-
clude low (1-2 mph) in-stand wind-
speeds. Wind direction can be
variable. Actual fine-fuel moisture
should be above 15 percent.
When underbuming, start with a
square ignition grid (equal distance
between spots within a line and between
flight lines). Two chains by 2 chains
is often used.
Always secure the downwind base
line first.
Be careful when underburning
stands with a flammable understory
or a heavy rough.
Severe crown scorch is likely if
fuel is too dry.
Under the same weather condi-
tions, fires in Piedmont fuel types
tend to spread slower and be less in-
tense than those in Coastal Plain fuel
The usual changes in weather dur-
ing a typical winter day may require
modification of ignition patterns

throughout the day. Burn until fires
verge on getting "too hot" Then either
quit burning or resort to backing
fires only.
a Continually modify the ignition
grid to take advantage of topography
and changes in understory fuels.
a Costs are low because firing is
rapid and no interior control lines
need to be constructed.

Aerial Ignition
When ground ignition techniques
are used, the downwind spots will
usually coalesce and burn out before
the whole block has been ignited. In
contrast, aerial firing permits ignition
of a block to be completed before the
downwind spots have burned out.
This does not present a problem at
the damp end of the prescribed burn-
ing window when actual fine-fuel
moisture is near 20 percent. Rapid
ignition of a block reduces both flying
time and the time needed to complete
the burn. However, when using aerial
ignition techniques under "traditional"
ideal burning conditions for line-
backing fires with actual fine-fuel
moisture near 10 percent, rapid igni-
tion of the entire area can result in an
increase in fire intensity to unaccep-
table levels. You would then have
little recourse except to let the area
burn out and hope that damage is
limited to just a loss in overstory
Some experienced burners start
firing early in the day, before the fuel
is dry enough to carry fire well.
They reduce the distance between
spots within a line to less than 2
chains by 2 chains. The increased
number of ignitions creates more heat
and helps dry the surface fuels,
especially when a helitorch is used.
The distance between spots must be
expanded as the morning progresses
and burning conditions improve.
Otherwise, the spots will merge
laterally forming lines of heading fire
that get too intense before reaching
the next downwind line of ignition
points. The distance between lines
can also be increased as necessary to
maintain a square ignition grid.
Current aerial ignition techniques
can be separated into two major
types: the DAID (Delayed Aerial
Ignition Device) or ping-pong ball
system, and the helitorch or flying
driptorch system. The ping-pong ball
system utilizes small plastic spheres

containing potassium permanganate.
The balls are injected with ethylene
glycol and immediately jettisoned
before the chemicals react thermally
to produce a flame that consumes the
ball. The dispensing machine can be
mounted in small airplanes or
helicopters. The ping-pong ball
system works best in continuous fuels
or in areas where a mosaic burn pat-
tern is desired.
The helitorch is simply a giant
driptorch and drum of gelled gasoline
mounted or slung under a helicopter.
The helitorch is well suited for
discontinuous fuels such as those in
clearcuts because this system emits a
steady stream of burning fuel globs.
It is very difficult to effectively
regulate the spacing between these
fuel globs. At least one gadget that
apparently solves this problem is
being marketed. Any helitorch not
modified to effectively control the
timing between the globs of burning
fuel should be considered a line-
firing device.
Both types of aerial ignition
dramatically reduce the time needed
for an area to burn out. Although
roughly the same amount of smoke is
produced, it is emitted over a shorter
period and more of it is entrained in
the convection column. Thus, the im-
pact of any adverse air quality effects
is much reduced.

Factors Associated with Aerial
Rapid firing and burnout allows
use of a much smaller prescription
Damp, fine fuels are of critical
importance. Actual fine-fuel
moistures of 15 to 25 percent are
Requires an experienced burning
boss to make ignition grid adjust-
ments and to determine when to halt
ignition due to conditions.
Although not likely under
prescribed fire conditions, too much
heat energy released over too short a
period will result in a sudden,
dangerous increase in fire intensity.
Large acreages can be safely
burned in a single burning period.
Many widely dispersed tracts can
be burned during a single day.
A contingency plan is essential in
the event the aircraft is reassigned or
equipment breaks down during

DAID (Delayed Aerial Ignition Device) dispenser mounted in helicopter

Helitorch in action

Factors Assoicated with Ping-pong
Ball (DAID) System
* Best suited for continuous fuels or
when a mosaic pattern is desired.
E Ignition spacing within and between
flight lines can be easily adjusted.
* A 2 by 2 chain to 4 by 4 chain
grid (one ignition point every 0.4
acre to one every 1.6 acres) works
well in both palmetto/gallberry and
Piedmont fuel types.
* When underburning Coastal Plain
fuel types, actual fine-fuel moisture
should be 20 to 25 percent (even
higher in very heavy fuels) and the
air temperature should be low,
preferably below 50F.
* In Piedmont fuel types, actual
fine-fuel moisture contents between
10 and 15 percent and air temperature
below 55F work well.
* Make sure no DAID's are
mistakenly dropped outside the burn
as the helicopter turns at the end of
each line.

Factors Associated with Helitorch
* Not as safe as the DAID system,
but less expensive.
* If the torch and fuel tank is slung
under rather than attached to the
helicopter, a larger crew will be
* Creates disposal problems.
* Very difficult to regulate spacing
within a flight line.
* Fuel-mixing viscosity is
sometimes inconsistent due to
temperature changes which, in turn,
further aggravate in-line spacing of
ignition spots.
* The most efficient firing technique
for large, cleared areas with discon-
tinuous fuels, including piled or win-
drowed debris.
* Use extreme caution when under-
burning Coastal Plain fuel types. Try
to keep within-line ignition point in-
terval to at least 2 chains.

Center and Circular
(Ring) Firing
This technique is useful on cut-
over areas where a hot fire is needed
to reduce or eliminate logging debris
prior to seeding or planting. It works
best when winds, if any, are light and
variable. This procedure should never
be used for underburning because of
the likelihood of severe tree damage
as the flame fronts merge
As with other burning techniques,
the downwind control line is the first
line to be ignited. Once the base line
is secured, the entire perimeter of the
area is ignited and the flame fronts
allowed to converge. One or more
spot fires are often ignited near the
center of the area and allowed to
develop before the perimeter of the
block is ignited. The convection
generated by these interior fires
creates indrafts that help pull the
outer circle of fire toward the center.
This firing method can generally be
used in any season, and weather con-
ditions are not as critical. However,
caution is in order, particularly when
the atmosphere is unstable. This type
of fire tends to develop a strong con-
vection column which can cause
spotting a considerable distance

Pile and Windrow
The objective of piling logging
debris before burning it is to prolong
fire residence time on a restricted
area so that larger materials have
time to be consumed. Some areas
will contain an unacceptable amount
of large, scattered debris that must be
concentrated to ensure consumption.
This material should be piled and not
windrowed. Windrowing can reduce
site quality by removing topsoil.
Piedmont soils are also susceptible to
compaction from the heavy equip-
ment used, especially during wet
weather. Full exposure of the soil to
the sun and rain bakes the top layer.
Furthermore, the direct force of rain-
drops will clog soil pores and often
results in erosion on steep slopes.
The area beneath the windows is lost
to production because the debris is
rarely consumed completely and what
remains makes planting difficult or
impossible. Even when windows
contain breaks spaced every couple of
chains, they still present a barrier to
firefighting equipment and wildlife.

Fire -



Ignite backing fire first, then center and then perimeter

Center firing technique

The biggest deterrent to window
burning, however, is that it causes a
high percentage of all smoke incidents.
Large volumes of fuel, including
larger pieces that contain a lot of
moisture, are consumed. However,
oxygen for good combustion is lack-
ing, especially in large piles and wide
windows. Large amounts of soil are
often mixed in, further compounding
the problem. The result is a fire that
continues to smolder for days or
weeks, creating air quality problems
because the smoke produced by
smoldering combustion is not hot
enough to rise into the atmosphere.
The smoke stays near the ground
where it cools even more, dirifting
and concentrating in low areas
because of cool air drainage. To
make matters worse, the smoke often
mixes with humid air to produce fog
which further reduces visibility.
Coupled with these problems is the
fact that the weather changes from
day to day making it impossible to
predict, and thus manage, the smoke
for more than a day or two. For these
reasons, air quality regulations pro-
hibit pile and window burning in

some areas.
Although it generally costs more
to pile than to window, piles are
preferable to windows because access
within the area is no problem, plant-
ing is easier, burning is safer and,
most important, smoke problems are
significantly reduced since piles burn
out much quicker! Generally, piles
contain less dirt and dry faster. Burn-
ing piles can easily be "bumped" to
remove any dirt and pushed in to in-
crease consumption. The whole area
can then be utilized.
Keep piles small and minimize the
amount of soil in them so surface
water can pass through, and the
debris can dry quickly. Always pile
when the ground surface is dry; less
soil compaction will take place, and
considerably less soil will end up in
the piles. Allow fresh logging debris
to cure first and to dry after rain.
Then "shake" the debris while piling
to remove as much soil as possible. If
material is piled while green or wet,
the centers of the piles take an ex-
ceedingly long time to dry. Piles that
contain little soil and are constructed
to allow some air movement will

Tractor-mounted firing device for piled-debris ignition

result in a burn that consumes
significantly more of the debris and
produces less smoke. More efficient
burning and greater heat output will
lift smoke higher, reducing smoke
concentrations near the ground. Burn
when the atmosphere is neutral to
slightly unstable, but not unstable
enough to create control problems.
Forest managers can take many
steps to minimize these debris pro-
blems. Much of the larger material
left after harvest is cull hardwood,
and periodic use of underburns during
the rotation will reduce the number
of large hardwoods at harvest. Some
of the cull material can often be sold
or given away as firewood. Sites
often can be prepared for seeding or
planting by a broadcast burn without
piling the debris. Trees should be cut
close to the ground, leaving low
Advances in harvesting equipment
and methods have also helped. Large
mobile harvesters chip the whole
tree, increasing utilization and reducing
the need for site preparation. Tree-
length logging and gate delimbing

(backing a drag-load of trees between
two posts) tend to concentrate much
of the debris at the logging deck.
Piles created in this manner are
generally free of soil (providing log-
ging was suspended in wet weather)
and can be burned as is.
Techniques used in burning piled
debris are somewhat fixed because of
the character and placement of fuel.
Traditionally, each pile is ignited
along its perimeter, but burnout can
be speeded up considerably by igniting
the pile center. A helitorch is often
used because burning globs of gelled
gas penetrate deep into piled fuels
and provide a "large" heat source.
Tractor-mounted ignition devices that
help burning fuel penetrate down
toward the center of a pile have also
been fabricated.

Factors Associated with Pile and
Windrow Burning:
* A large majority of all smoke-
related incidents are caused by this
type of burning.
* Produces the most smoke of all
firing techniques.

* Burns can continue to smolder for
many weeks.
* Smoke produced at night tends to
stay near the ground.
* Cannot be readily extinguished
after ignition. If extinguished, even
more effort is required to reignite
them the next day.
* Can burn in light or variable
* Usually safe and easy to control,
provided piles are not next to the
edge of the area and are not left unat-
tended, particularly when burning
during periods of high fire danger.
* Piles should be as free of soil as
* Fuel should be dry.
* Burn area should be as small as
economically practical.
* Need neutral to unstable condi-
tions for good smoke dispersion -
which generally do not occur after
* Need good mixing heights and
transport winds.

Dirt In windows can aggravate smoke management

Windrows can smolder for long periods of time

Piles bum more efficiently than windows



Prescribed burning helps achieve
many desired resource objectives, but
it nevertheless pollutes the air. We
therefore have an obligation to mini-
mize adverse environmental effects. If
this obligation is disregarded, pre-
scribed burners can be held liable for
damages from accidents or problems
resulting from their actions. Use the
following guidelines to reduce the
impact from smoke.

A. Define objectives.-Be sure you
have clear resource objectives and
have considered both on-site and off-
site environmental impacts.
B. Obtain and use weather and
smoke management forecasts.-
Weather information, and fire-
weather and smoke management
forecasts are available to all resource
managers through State forestry
agencies. Be sure to use them. Such
information is needed to predict
smoke generation and movement as

well as fire behavior. If the forestry
weather outlook does not agree
reasonably well with the radio/TV
forecast, find out why.
C. Don't burn during pollution
alerts or stagnant conditions. -
Smoke will tend to stay near the
ground and will not disperse readily.
Many fire-weather forecasters include
this in their regular forecasts.
D. Comply with air pollution control
regulations.-Know the regulations
that apply at the proposed burn site
when you make the prescription.
Check with your State fire control
E. Burn when conditions are good
for rapid dispersion.-Ideally, the
atmosphere should be thermally
neutral to slightly unstable so smoke
will rise and dissipate, but not so
unstable as to cause a control prob-
lem. Again, your local forestry agency
can help. Some States use Category
Day based on the ventilation rate, but

if the Dispersion Index is calculated
for your area, it is a better indicator
(see table 1). Reassess a decision to
burn when the daytime Dispersion
Index value is below 41.
F. Use caution when near or upwind
of smoke-sensitive areas.-Burning
should be done when wind will carry
smoke away from public roads, air-
ports, and populated areas. Do not
burn if a smoke-sensitive area is
within 1/2 mile downwind of the pro-
posed burn.
G. Use caution when smoke-
sensitive areas are down drainage.-
Minimize the production of residual
smoke. Use aggressive mopup as

Prescribed Fire Reduces Air
Pollution From Wildfires

TABLE 1.-Relationship of Dispersion Index to
On-the-Ground Burning Conditions

Index Burning conditions

>100 Very good Burning conditions may be so good that fires may be
hazardous and present fire control problems. Reassess decision to burn.
61 100 Good preferred range for prescription burns.
41 60 Generally OK climatological afternoon values in most inland forested
areas fall in this range.
21 -40 Fair stagnation may be indicated if accompanied by low windspeeds.
Reassess decision to burn.
13 20 Generally poor do not burn. Stagnant if persistent, although better than
average for a night value.
7- 12 Poor do not bur. Stagnant during the day, but near or above average at
1 -6 Very poor represents the majority of nights at many locations.

H. Estimate the amount and con-
centration of smoke you expect to
generate.-This guideline is especially
important near highways and populated
areas (see table 2). Smoke manage-
ment guidelines will help you develop
this estimate. Some States tie
allowable smoke generation to
Category Day.
I. Notify your local fire control
office, nearby residents, and adja-
cent landowners. -Notification is
common courtesy and is required in
most areas. People need to know that
your burn is not a wildfire. In addi-
tion, the burner will get advance
notice of any adverse public reaction
and be made aware of special prob-
lems, such as respiratory ailments,
washday, etc.
J. Use test fires to confirm smoke
behavior.-Set these in or adjacent to
the area proposed for burning, away
from roads or other edge effects.
K. Use backing fires when possible. -
Backing fires consume dead fuels
more completely and produce less
smoke. Even though slower and more
expensive, they produce fewer
pollutants and restrict visibility less.
L. Burn during middle of the day
when possible.-Atmospheric condi-
tions for dispersion of smoke will be
most favorable.
M. Consider burning in small
blocks if Dispersion Index is below
61.-The larger the area being burned,
the higher the concentration of parti-
culates put into the air, and the
longer the duration of the visibility
reduction downwind. However, if
weather conditions are good for rapid
smoke dispersion, e.g., the Disper-
sion Index is above 60, it is often
better to burn the whole area at one
time from a smoke management
N. Do not ignite organic soils.-It is
virtually impossible to put out an
organic soil fire without submerging
it in water. It will smoke for weeks
despite control efforts, creating severe
smoke problems for miles around.
Such fires can also reignite surface
fuels, resulting in a wildfire.
O. Be very cautious ofnighttime
burning.-Smoke drift and visibility
are very difficult to predict at night.
The wind may lessen or stop com-
pletely keeping smoke concentrations
high in the vicinity of the burn. Burn
at night only when you have a definite
forecast of optimum conditions. A

TABLE 2--Effect of Smoke Concentration on Visibility

Smoke concentration Visibility
(micrograms/m') (miles)'
125 2.0 8
250 1.0- 4
500 0.5 -2
1,000 0.25 1
'These numbers only valid when relative humidity is below 70 percent.

nighttime smoke patrol is often
P. Anticipate down-drainage smoke
flow.-Atmospheric conditions tend to
become stable at night. Stable condi-
tions tend to keep smoke near the
ground. In addition, downslope winds
generally prevail at night. Thus, smoke
will flow down drainage and concen-
trate in low areas. When relative
humidity rises above 80 percent and
smoke is present, the formation of
fog becomes increasingly likely as
moisture condenses on the smoke
particles. There seldom are satisfac-
tory solutions to these problems, so
they should be avoided entirely
whenever possible.
Q. Mopup along roads.-Start mopup
along roads as soon as possible to
reduce impact on visibility. Ex-
tinguish all stumps, snags and logs.
Mopup should be particularly ag-
gressive whenever roads are in areas
where smoke could travel downslope
or up or down a drainage.
R. Have an emergency plan.-Be
prepared to extinguish a prescribed
burn if it is not burning according to
plan or if weather conditions change.
Have warning signs available. If wind
direction changes, be prepared to
quickly contact the local law enforce-
ment agency and to direct traffic on
affected roads until traffic control
personnel arrive.

Caution: Check For Down
Drainage Smoke Flow At Night!

Screening System for
Managing Smoke
Most southern States have either
voluntary or mandatory smoke
management guidelines that should
be followed when planning a pre-
scribed burn. Your local State forestry
office can advise you of recommended
or required procedures. Many of
these guidelines use a term called the
ventilation rate or ventilation factor
which estimates the atmosphere's
capacity to disperse smoke. Another
way to estimate this capacity is to use
the Dispersion Index (see table 1)
developed at the Southern Forest Fire
Laboratory. This calculated index is
better able to incorporate diurnal
changes in the lower atmosphere.
If you will be burning in a State
that has not issued guidelines, use the
Southern Forestry Smoke Management
Guidebook (see Suggested Reading
section, second listing under U.S.
Department of Agriculture). This
guidebook tells you how to predict
smoke concentrations at any distance
downwind. An improved and com-
puterized version, called PRESMOK,
simplifies use of this prediction
system. Copies are available from the
Southern Forest Fire Laboratory. Use
of this smoke screening system does
not take precedence over State
guidelines. The full system cannot be
discussed here, but an updated version
of the Initial Screening System based
on the Guidebook is presented below.
This system has five steps: (1) Plot
direction of the smoke plume, (2)
Identify smoke-sensitive areas, (3)
Identify critical smoke-sensitive
areas, (4) Determine fuel type, and
(5) Minimize risk.

Figure A

Step 1. Plot Direction of the Smoke
A. Use maps on which the locations of
smoke-sensitive areas can be iden-
tified. Plot the anticipated down-
wind smoke movement a distance
of: 5 miles for grass fuels
regardless of fire type; 10 miles
for palmetto-gallberry fuels when
using line-backing fires or spot
fires; 20 miles for palmetto-
gallberry fuels using line-heading
fires; 30 miles for all logging
debris fires; 5 miles for line back-
ing fires in all other fuel types;
and 10 miles for line-heading fires
in all other fuel types, or burns of
250 acres or more. First locate
the planned burn area on a map
and draw a line representing the
centerline of the path of the
smoke plume (direction of
transport wind) for the distance
indicated. If the burn will last 3
or more hours, draw another line
showing predicted wind direction
at completion of the burn.
B. To allow for horizontal dispersion
of smoke as well as shifts in wind
direction, draw two other lines
from the fire at an angle of 30
degrees from the centerline(s) of
observed wind direction (45
degrees if forecast wind direction
used). If fire is represented as a
spot, draw as in figure A. If
larger, draw as in figure B. The
result is your probable daytime
smoke impact area.
C. Now go down-drainage for one-
half the distance determined
above, but do not spread out except
to cover any valleys or bottoms.
The result is your probable night-
time impact area, providing the
burn will be completed at least 3
hours before sunset, and providing
the forecast night winds are light
and variable.

Step 2. Identify Smoke-Sensitive
Identify and mark any smoke-
sensitive areas (such as airports,
highways, communities, recreation
areas, schools, hospitals, and factories)
within the impact zone plotted in step 1.
These areas are potential targets for
smoke from your burn.
A. If no potential targets are found,
you may burn as prescribed.
B. If the area to be burned contains
organic soils that are likely to
ignite, do not burn.
C. If any targets are found, continue
this screening system.

Step 3. Identify Critical Smoke-
Sensitive Areas
A. Critical smoke-sensitive areas are:
1. Those that already have an air
pollution or visibility problem.
2. Those within the probable
smoke impact area as determined
below. If the distance determined
in step 1 was:
a) 5 miles, any smoke-sensitive
area within 1/2 mile is critical,
both downwind and down-
b) 10 miles, any smoke-sensitive
area within 1 mile is critical.
c) 20 miles, any smoke-sensitive
area within 2 miles is critical.
d) 30 miles, any smoke-sensitive
area within 3 miles is critical.
B. If any critical smoke-sensitive
areas are located, DO NOT
BURN under present prescription!
1. Prescribe a new wind direction
that will avoid such targets and
return to the beginning of this
screening system, or
2. If smoke-sensitive area is in last
half of distance criteria, reduce

the size of the area to be burn-
ed by approximately one half,
complete burn at least 3 hours
before sunset, and aggressively
mopup and monitor, or
3. Use an alternative other than

C. If no critical smoke-sensitive areas
are found, or criteria BI or B2 is
met, continue the screening system.

Step 4. Determine Fuel Type
The smoke produced may vary
greatly by type, amount, and condi-
tion of fuel consumed.
A. From the list below determine
which broad type best fits your
1. Grass (with pine overstory)
2. Light brush
3. Pine needle litter
4. Palemetto-gallberry
5. Windrowed logging debris
6. Scattered logging debris or
small dry piles

B. Review fuel categories or
1. If the fuel type is described by
one of the above categories,
2. If your fuel type is not com-
parable to any of the above,
pick the fuel type for which
fire behavior and smoke pro-
duction most nearly compare
with yours and proceed with
first few burns.

C. If the fuel type is windrowed log-
ging debris, and you have identi-
fied smoke-sensitive areas, DO
NOT BURN under present
prescription. Smoke production is
great and can last for weeks.

Figure B

1. Prescribe a new wind direction
to avoid all smoke-sensitive
areas and return to the beginning
of the system.
2. If you cannot avoid all smoke-
sensitive areas, you will need a
better procedure than this sim-
ple screening system. Refer to
the Southern Forestry Smoke
Management Guidebook or

D. If the fuel type is scattered log-
ging debris or small, essentially
dirt-free, dry piles, the following
conditions should be met:
1. Size of area to burn less than
100 acres.
2. No major highways within 5
miles down drainage.
3. No other smoke-sensitive areas
within 3 miles down drainage.
4. If relative humidity is predicted
to stay below 80 percent and
surface winds above 4 m.p.h.
all night, the distances in 2 and
3 above can be cut in half.

E. If your comparable fuel type is
one listed in 4A above, determine
your total per-acre fuel loading.
See below or Southern Forestry
Smoke Management Guidebook
for tables to assist you.
1. If less than 10 tons per acre,
continue. Generally, the total
fuel loading will be less than
10 tons in the fuel types listed
below when age of rough is:
a. Grass (with pine overstory),
any age. Also wheat fields
and other agricultural burns.
b. Light brush, 7 years old or
less (10 years if basal area is
under 100 square feet per
c. Loblolly pine with
a. palmetto-gallberry
understory, 7 years or less
if basal area is under 150
square feet per acre.
b. little or no understory, 15
years or less if basal area
is under 150 square feet
per acre.
d. Slash pine with
a. palmetto-gallberry
understory, 5 years or less
if basal area is under 150
square feet per acre.
b. little or no understory, 8
years or less if basal area
is under 150 square feet
per acre.

2. If greater than 10 tons per acre,
refer to the Southern Forestry
Smoke Management
Guidebook or double the
distance determined in step 1A.
Use 1 1/2 times the distance if
close to 10 tons.

Step 5. Minimize Risk
To meet your smoke management
obligations when any smoke-sensitive
area may be affected by your burn,
you must meet all of the following
criteria to minimize any possible
adverse effects.

* Height of mixing layer (mixing
height) is 1,650 feet (500 meters)
or greater.
* Transport windspeed is 9 mph (4
meters per second) or greater.
* Background visibility is at least 5
miles within the plotted area.
* If rough is older than 2 years, use
a backing fire. If burn can be
completed 3 hours before sunset,
or if no smoke-sensitive areas are
located in the first half of the
impact area, other firing techni-
ques can be used.
* Promptly mopup and monitor to
minimize smoke hazards.
If a smoke-sensitive area is in the
overlapping trajectory of two
smoke plumes, it should be 1 mile
from either source (2 miles if one
is from logging debris).
For night bums, backing fires
with surface windspeed greater
than 4 mph and relative humidity
under 80 percent should be
E If it appears that stumps, snags,
or logs may cause a residual
smoke problem, take steps to keep
them from burning. If they do
ignite, extinguish them.
Daytime value of the Dispersion
Index between 41 and 60 is ade-
quate for small fires and low levels
of burning activity. As either siZe
of individual fires or level of burning
activity increases, the Dispersion
Index value should also increase.

Many variables affect the behavior
and resulting smoke from a prescribed
bur. The above system works best in
flat terrain and was not designed for
use in mountainous country. It does
not attempt to consider all the variables:
it can only offer broad guidelines. If
your prescribed fire complies with all
conditions in these five steps, you
should be able to safely burn without
causing a smoke problem. If you
have any marginal answers, areas that
are especially sensitive to smoke,
heavy fuel loadings or wet fuels, use
the prediction system mentioned in
the Southern Forestry Smoke
Management Guidebook. You must
make the final judgement.

CAUTION: Be Sure Atmospheric
Conditions Are Conducive
To Good Dispersion!

Planning the

Prescribed Burn

The first step to a successful
prescribed burn is a stand-by-stand
analysis of your forest lands. Deter-
mine the needs of each stand and what
acitons should be taken to meet these
needs. Prescribed fire as well as other
alternatives should be addressed here
and a decision reached regarding the
preferred treatment.
Prescription burning is a highly
technical job requiring knowledge of
fire behavior, suppression techniques,
and environmental effects of fire.
Well in advance of the burning season,
scout stands that may need a fire
treatment and choose those to burn.
Overplan the number of acres to be
burned by 10 to 25 percent so substi-
tutions can be made if necessary, and
so additional areas can be burned if
favorable weather continues. The
number of suitable burning days
varies widely from year to year and
the acreage that can be burned on a

given day can be increased drama-
tically if aerial ignition is used. If
you have several blocks to burn, set
priorities. Specifically designate any
planned burns that require exacting
weather conditions. Considerations
include heavy fuels, small trees,
potential smoke problems, etc. Indi-
cate all blocks to be burned on an
administrative map. When the burns
are completed, record the dates on
the map.
A written prescribed-burning plan
prepared by a knowledgeable person
is needed for each area to be burned.
Complete the plan before the burning
season and be prepared to burn when
the prescribed weather occurs. Some
plans may be quite short and simple
while others will be complex. Indivi-
dual blocks can vary from a few
acres to over 1,000, but topography,
and amount and type of fuel in a unit
should be similar. Your plan can con-

sist of a series of blocks in the same
compartment or management unit as
long as the same objectives apply and
the fuel is similar.
Break large areas into 1-day burning
blocks or smaller areas. Use existing
barriers such as roads and creeks as
possible, but be sure these barriers
are effective at the time of the burn.

The Written Plan
A prepared form with space for all
needed information is best. The form
will serve as a checklist to be sure
you have not overlooked some aspect
or potential impact. Sample forms for
both understory burs and postharvest
burns can be found on pages 34, 35,
and 36. The "simple" form can be
used on small burs within a large
landholding that does not contain
public roadways. Contents of the writ-
ten plan should include:

TABLE 3 Effects of Age of Rough on Some Common Fire Parameters

Parameter Age of rough (years)
1 2 4 8 16
Litter fuels (tons/ac) 15 3 25 45 4-7.5 55 12 15
Fireline intensity B' 8 15 12 25 20 35 25-65 30-75
(Btu/sec/ft) H' 30 60 50 90 80 145 Outside Rx underburning window

Flame length B 0.5- 15 1 -2 15-2.5 2-3 2-3.5
(feet) H 1.5 2 2 2.5 2.5 3.5 Outside Rx underburning window

Scorch height' B <5 <5- 5 <5- 7 5-11 6-12
(feet) H 6 10 9 14 13 19 Outside Rx underburning window

Assume a 20-year-old southern pine plantation on the Coastal Plain with no understory present. Table values will increase as the
amount of understory increases. In the Piedmont and mountains, an understory is likely to have an opposite effect except during
severe drought.

'B = Backing fire with rate-of-spread of 100 feet per hour and fuel consumption of 60 percent.
'H = Heading fire with rate-of-spread of 660 feet per hour and fuel consumption of 40 percent.
'Ambient temperature of 500F and windspeed of 2mph. Lower temperatures and higher windspeeds will decrease scorch height.

Simple Understory Prescribed Burning Unit Plan

Landowner Permit no.
Address Phone No.
S T R_ County Acres to Burn Previous burn date
Purpose of burn
(Draw map on back or attach)

Stand Description
Overstory type & Size
Understory type & height
Dead fuels: description and amount

Height to bottom of crown

Preburn Factors
Manpower & equipment needs
List smoke-sensitive areas & locate on map
.noial nrflfal itionn

Estimated no. hours to complete Passed smoke screening system
Adjacent landowners to notify

Weather Factors: Desired Range
Surface winds (speed & dir.)
Transport winds (speed & dir.)
Minimum mixing height
Dispersionlstagnation index
Minimum relative humidity
Maximum temperature
Fine-fuel moisture (%)
Days since rain Amount

Fire Behavior: Desired Range
Type fire
Best month to burn
Flame length
Rate of spread
Inches of litter to leave

Evalution: Immediate
Any escapes? Acreage
Objective met
Smoke problems
% of area with crown discoloration of
5-25% 26-50% 51-75% 76%+ _
Live crown consumption
% understory veg. consumed
Adverse publicity
Technique used OK




Date burned

Evaluation by
Insect/disease dam.
Crop tree mortality
/% understory kill
Soil movement
Other adverse effects


Prescription made by

Title Date / /

Understory Prescribed Burning Unit Plan

Prepared by Signature Date Permit no.
State County District Comp't
Burning unit no. S T R Gross acres Net acres
Landowner Address & phone no.
Person responsible & how to contact day & night
(Draw map on back or attach)
A. Record of Previous Burning: Date Fire type Results
B. Description of Stand:
1. Overstory: Type, density, size Height to bottom of crown
2. Understory: Type, density, height
3 Dead fuels: Type, density, age, volume
4. Soil type and topography
C. Purpose(s) of Burn:
D. Specific Objectives:
E. Preburn Factors:
1. Chains to plow (see map): Exterior Interior Total
2. Chains to fire (see map): Exterior Interior Total
3 Crew size: Equip. needs
4. Estimated tons/acre Total tons to be burned
5. Ignition procedure (see map)
6 Passed screening system? Special precautions

7 Notify:

8. Regulations that apply
9. List smoke-sensitive areas & critical targets (see map):

F. Weather Factors: Desired Range
1. Surface wind (speed & dir)
2. Transport wind (speed & dir.)
3 Stability/stagnation index
4. Minimum mixing height
5. Dispersion index
6. Minimum relative humidity
7. Maximum temperature
8. Fine-fuel moisture
9. Days since rain __ Amount _
10. Burning Index__ Drought Index
G. Fire Behavior: Desired Range
1. Type fire
2. Best month to burn
a Time of day to start
4. No. hours to complete
5. Flame length
6 Rate of spread
7. Fireline intensity
& Inches of litter to leave
H. Evalution Immediately After Burn:
1. Acres burned
2. Spotting_ Distance
3 Any escapes
4. Objectives met
5. Smoke problems
6. % understory veg. consumed
7 % of area with crown discoloration of
5-25% 26-50% 51-75% 76%+ _
8. Live crown consumption
9. Adverse publicity
10. Remarks



Actual Range

Date burned
Time Set

Litter left
Future Evaluation:
Evaluation by
Date made
Insect/disease dam.

Crop tree mortality

/o% Understory kill
Soil movement
Other adverse effects


Actual Range


Postharvest Prescribed Burning Unit Plan

Prepared by Signature Date Permit no.
State County District Comp't
Burning Unit No. S T R Gross acres Net acres
Landowner Address & phone no.
Person responsible & how to contact day & night
(Draw map on back or attach)
A. Description of Area:
1, Natural stand or plantation Stand age Harvest date
2. Clearcut Harvest method Pine basal area removed
3 Organic soil Hardwood basal area Hardwoods utilized
4. Unmerchantable trees felled Snags felled Debris evenly distributed
5. Debris (light, medium or heavy) Brush (light, medium or heavy)
6 Herbaceous fuels (light, medium, heavy) Herbaceous fuels continuous
7 Herbicide used Date applied I I
a Drum chopped Single or Double Pass Date Completed I
9. Windrowed and/or piled Date piled / / Piled when wet
10. Pile or window dimensions: Ht. Width (dia.)
11. Windrow break interval
B. Preburn Factors and Desired Fire Intensity:
1. Areas to exclude:
2. Chains to plow (see map): Exterior Interior Total
a Chains to fire (see map): Exterior Interior Total
4. Equipment needs
5. Crew size Type of fire Type of ignition
6. Ignition procedure (see map):
7. No. of hours to complete Tons/acre to consume Litter to leave (in.)
8 Special precautions:

9. Notify:

10. Regulations that apply
11. Passed screening system? List smoke-sensitive areas, critical targets &

locate on map:

C. Weather Factors: Desired Range Predicted Actual
1. Surface wind (speed & dir.)
2. Transport wind (speed & dir)
3 Mixing height
4. Dispersion Index (or comparable)
5. Relative humidity (%)
6. Temperature (oF)
7. Fine-Fuel moisture (%)
8 10-hr. fuel moisture (%)
9. Days since rain Amount
10. Burning Index Drought Index
11. Best month to burn Dates burned
12. Time of day to start Time set
D. Summary of Burn:
1. Type fire & ignition
2. All piles, windows & logging decks ignited
3 % of area burned Did area between piles burn?
4. Spotting frequency Distance firebrand material
E. Evaluation Immediately After Burn:
1. Any escapes: Number Adjacent to burn area? Acres involved
2. Hours to burnout: Active flaming Smoldering Total hours
3. % understory veg. consumed Depth of litter remaining (in.)
4. % material < 3" dia. consumed Did piled debris burn down?
5. Objectives met
6. Adverse publicity
7. Smoke problems
a Remarks
F. Future Evaluation (Date, signature and remarks)

Required Signatures
Provide spaces for signatures) of
persons) who prepared the plan. This
identifies the people who know the most
about the plan.

Purpose and Objective(s)
Include in the written plan the
reasons) for prescribing a fire.
Examples include: prepare seedbed,
control insects or disease, reduce
hazard, improve wildlife habitat, con-
trol understory, improve forage,
increase accessibility, and enhance
aesthetics. In addition, give a specific
quantifiable objective. State exactly
what the fire is to do what it
should kill or consume, how much
litter should be left, etc. Also con-
cisely describe the expected fire
behavior, including the desired range
in flame length and fireline intensity.
In case prescribed weather conditions
do not materialize, this description
may allow the objectives) to still be
achieved by varying the firing tech-
nique. Such information will also be
useful in determining success of a

Map of the Burning Unit
A detailed map of each burning
unit is an important part of the burning
plan. The map should show the boun-
daries of the planned burn, adjacent
land owners, topography, control lines
(both existing and those to construct),
anticipated direction of the smoke
plume, smoke-sensitive areas, holding
details, and other essential informa-
tion. Plowed control lines are often
not necessary. Consider expanding the
planned burn to employ existing fire-
breaks and natural barriers. For exam-
ple, use fuel type boundaries such as
occur near creek bottoms where the
fire will go out as it encounters fuels
with a higher moisture content. Show
areas that should be excluded or pro-
tected such as improvements, young
reproduction, sawdust piles, etc. Sub-
divide each area to be burned into
logical, 1-day burning blocks, or
smaller areas if smoke management
needs dictate.

Equipment and Personnel
List equipment and personnel needed
on site and on standby. Assign duties.

Fire Prescription
The amount of fuel, weather condi-
tions and desired intensity of the burn
will determine the firing technique

Make a prescribeire plan for each area
Make a prescribed fire plan for each area

J. Taylor Land
Burning unit map

and ignition pattern to use. Species
involved and height of overstory will
determine the maximum intensity that
can be tolerated. Where large amounts
of fuel are present, cooler burns can
be accomplished by burning when
humidity and fuel moisture are near
the high end of the range so a smaller

fraction of the fuel will burn. Lower
temperatures are desirable with more
intense fires, especially when under-
story fuels are tall.
A series of user-friendly computer
programs called BEHAVE has been
developed to predict the behavior of a
fire. They are based on a specific set

of fuel data and prescribed weather
conditions. These programs will run
on a hand-held calculator with a fire
behavior CROM (Custom Read Only
Memory). You can use them in the
field to make instant decisions as
burning conditions change. A version
called MICRO BEHAVE, compatible
with IBM PCs, is also available at
very low cost from Forest Resources
Systems Institute (FORS), Courtview
Towers, Suite 24, 201 N. Pine Street,
Florence, AL 35630; telephone (205)
Always think about smoke
management. Make sure your burning
plan passes a smoke management

Winter Most understory burning
is done during the winter dormant
season. Acceptable relative humidity,
temperature, fuel moisture, and steady,
persistent winds most often occur
Spring More variable weather
and generally higher fire danger dic-
tate smaller burns in the spring.
Check with local wildlife specialists to
avoid periods when prescribed burning
could harm nesting wildlife. Pine
buds are more exposed and thus more
susceptible to heat damage during
Summer Hot weather during the
summer means much less heat is
needed to raise the temperature of
plant tissue to lethal levels. For this
reason, summer burns are used to kill
undesirable hardwoods usually a
series of burs after an initial winter
bur. Care must be taken not to
severely scorch overstory crowns.
Postharvest burns to dispose of log-
ging debris can be conducted year-
round, but conditions are especially
good in mid to late summer because
the high ambient temperatures help
dry out the larger materials.
Fall Exercise special care when
burning in early fall just prior to the
dormant season. Both loblolly and
slash pines are more likely to die if
severely scorched or root damaged at
this time.

Time of Day
Normally, plan burning operations
so the entire job can be completed
within a standard workday. Prescribed
fires usually are ignited between 10
a.m. and noon, after sunshine has
evaporated any early morning dew. If
an inversion occurred the previous
night, wait until daytime heating
eliminates it before igniting the fire. If
the forecast is for poor nighttime
dispersion, halt ground ignition before
3 p.m. standard time (ST). Halt aerial
ignition before 4 p.m. ST, to allow
adequate time for the fire to burn out
before atmospheric dispersion condi-
tions deteriorate.
Burning conditions are usually bet-
ter during the day than at night because
windspeed is higher and wind direc-
tion steadier. Smoke management is
also much easier during the day. At
night smoke tends to stay close to the
ground and collect in depressions.
Also, relative humidity usually in-
creases at night, resulting in spotty
burning and an increased likelihood
that fog will form.
However, on winter nights when a
strong cold front moves across an
area, winds remain strong and persis-
tent and relative humidity does not
rise greatly. These conditions can pro-
vide good prescribed burning weather,
especially when cooler temperatures
are needed. Whenever night burning
is done, keep a close check on wind,
humidity, and smoke drift.

Firing Plan
Key parts of a successful prescribed
burn are plans for firing and holding
a burn. This plan should consist of a
narrative section and a detailed map.
The burning unit map is ideal for this
purpose because it already contains
much pertinent information. Add the
following items:
* Firing technique, ignition pattern,
and planned ignition time.
Manpower and equipment
needed, and planned distribution
for setting, holding, patrolling,
and mopping up the fire and
managing the smoke.
Location and number of reinforce-
ments and equipment that can be
mobilized rapidly if fire escapes.
Instructions for all supervisory
personnel, including complete
description or illustration of
assignment, and forces needed to
fire out, hold, and mopup the

Alternative Prescriptions
Consider alternative sets of weather
conditions (wind, relative humidity,
and/or fuel moisture) and methods of
burning that will produce a fire of
about the same intensity and accomplish
the desired objectives. Two separate
burns may be necessary to eliminate
heavy volumes of fuel without damage
to the overstory.

Preparation Work and Protection of
Sensitive Features
Include fire lines to be constructed,
snags to be lined or felled, special
features to be protected and the instal-
lation of any monitoring equipment.
Give instructions for the protection of
sensitive areas. Consider historical
and archeological sites, streams,
habitats of threatened and endangered
species, and fragile soils.
Notification of Intent to Burn
List the names and telephone numbers
of the local State fire protection officer
and other officials who should be
contacted prior to the bur. Make
direct contact with all homes and
businesses in the area likely to be
impacted by the burn. Offer to
evacuate anyone with respiratory prob-
lems during the burn. Put them up in
a local motel if necessary. Consider
written notification explaining the
reasons for the bur and encouraging
individuals with respiratory ailments
to contact you include a 24 hour
telephone number. Establish respon-
sibility for burn-day contacts and how
they will be made. Consider a news-
paper article describing the reasons
for the bum if you expect to produce
lots of smoke or anticipate any
negative reactions.

Establish Burn Acreage Goals
But NOT Quotas!

Impact of Smoke
List any sensitive areas near to,
downwind, or down drainage of the
bur. Include smoke management
strategies of avoidance, emission
reduction, dispersal, or all three, to
minimize any adverse smoke impacts.
Attach the smoke management plan
(e.g. screening system calculations) as
part of the burning plan.

Legal Requirements
List any legal requirements that might
apply, and what the prescribed burner
must do to comply. Remember, the
person who conducts the prescribed
burning operation may not be the one
who made the analysis and prepared
the prescription. Follow all applicable
statutes, regulations, and agency pro-
cedures. Needs for a written prescribed
burning plan, documentation of devia-
tions from the plan, and good judge-
ment cannot be overemphasized. Er-
roneous forecasts, unforeseen local
influences, and accidents occur despite
our best efforts to prevent them. Pro-
per documentation will help establish
that the prescribed fire was conducted
in a prudent and professional manner.
If a prescribed fire results in damage
or bodily harm and you cut covers,
neglected any mandatory require-
ments, or acted with disregard to the
welfare of others, you are likely to be
held responsible, regardless of whether
compliance would have changed the
outcome. For more information see
the summary article, Legal Implica-
tions of Prescribed Burning in the
South by William C. Seigal, listed in
the Suggested Reading section.

Escaped-Fire Plan
Identify potential fire escapes and
specify actions to take should such
occur. Designate who will be in
charge of suppression action and what
personnel and equipment will be

Control and Mopup
A plan must include necessary
safeguards to confine the fire to the
prescribed area and reduce smoke
impact. Mopup promptly and com-
pletely. Emphasize protection of all
adjacent land. Consider and make
plans for any variation in forecasted
weather that may change a prescribed
fire into a damaging wildfire, increase
the pollution in smoke-sensitive areas,
or create visibility problems on adja-
cent roads.

Include space for a written evalua-
tion of the prescribed burn. A record
of actual weather conditions, behavior
of the fire, and total environmental
effects of the bum is essential. This
information is used to determine the
effectiveness of the prescribed burn
and in setting criteria for future burns.
At the beginning of the prescribed
bur, record windspeed and direction,
fuel moisture, humidity, burning in-
dex, temperature, days since and
amount of last rain, and dampness of
soil and lower litter. Also record fire
behavior data such as type of fire
used, length of flames, and forward
rate of spread. Continue to record
applicable weather and fire-behavior
parameters at 2- to 3-hour intervals
throughout the bur. After the bum,
record amount of crown scorch, con-
sumption of brush, litter, and duff,
and any other evidence of fire intensity
such as unburned areas, exposed
mineral soil, and cracks in bark or
cupping on the lower bole due to bark
consumption. Also include a short
narrative on success of the burn.

Prescribed Fires Often Behave
Erratically At Edges Of Openings

Give Prescribed Burning FIRST
Priority When Weather Conditions
Are Favorable

1 0j <

Eddies caused by forest openings

Convection and eddies for open areas

Preparing for the

Prescribed Burn

Steps to Be Considered
Good preparation is the key to
successful burning. It is essential in
realizing maximum net benefits at
acceptable cost. Preparation consists
of all steps necessary in making the
area ready for firing and of having all
needed tools and equipment in operating
order and ready to go.
This preburn work is often done
by a crew consisting of a leader, a
tractor operator, and a cleanup per-
son. The leader should be trained
and experienced in prescribed fire.
The job is to locate and establish
control lines to best accomplish the
objectives of the burning plan. To do
this job skillfully, the leader must
have personal knowledge or informa-
tion available about:
* Weather elements involved
* Fire behavior
* Smoke management
a Amount and type of fuel on the
* Location of natural and manmade
fire barriers
* Degree of risk and hazard present
* Burning technique and intensity of
fire to be used
* Burning objectives for the par-
ticular area
* Restrictive measures dictated by
law or local custom
* Fire suppression safety
* Location of any improvements
which.could be endangered
* Areas within the prescribed unit
that may need to be excluded from
fire, such as:
areas with extreme mopup or
breakover potential (sawdust
piles, snags, etc.)
highly scenic areas
highly erodible areas
streamside zones
areas harboring special-quality
wildlife or plant community
habitat that would be damaged
by fire
desirable hardwood areas
timber and grass areas sus-
ceptible to fire damage

Establishing a control line in heavy rough

All site-specific information
should be included in the written
prescription. Before starting work,
the leader should inspect the area by
walking over it and should give safety
instructions to the crew.

Establishing Control
Plow in advance of burning,
preferably after leaf fall, to reduce
effect of fallen material on prepared
* Use natural barriers such as
streams, logging roads, or cultivated
fields whenever possible.
* Hold plowlines to a minimum,
keeping them shallow and on the con-
tour as much as possible in hilly
country. Consider igniting from wet
lines. Use skid trails and logging
roads where feasible.
* Keep control lines as straight as
possible. Bend them around excluded
areas, avoiding abrupt changes in
* Avoid rock outcrops and boggy
* Double or widen plow lines at
hazardous places.

* Subdivide large areas into logical
1-day burning jobs.
* Avoid leaving dense timber stands
or heavy fuel pockets near lines.
After Plow Lines are
* Remove any material above the
line that could carry fire across the
control line such as vines and
overhanging brush.
* Fall snags near line (inside and
* Construct water bars and leadoff
ditches in steeper terrain to prevent
soil erosion.
* Seed and fertilize exposed soil on
plow lines in steep topography to pre-
vent soil erosion.

Burning-unit Map
* Locate all control lines on the map
noting any changes from the original
* Note on the map any danger spots
along control lines having potential for
fire escape.

Executing the Burn

There are few days of good
prescribed burning weather during
the year. When these days arrive,
give top priority to burning. With
adequate preparation, burning can
begin without loss of opportunity.
A prescribed burning crew con-
sisting of a burning boss and 3 to 6
crew members can handle a burn of
several hundred acres. The leader
should be an experienced prescribed
burner with an understanding of fire
behavior. Such a crew often consists
of 3 torch people equipped with hand
tools, and a tractor operator with a
plow unit for emergency use. If aerial
ignition is used, the ground crew
often consists of a tractor-plow unit
and a 2-person crew with 2 pickups.
The aerial crew generally consists of
a pilot and machine operator when
the ping-pong ball system is used. If
the pilot is not an experienced fire
behavior observer, the burning boss
should also be in the helicopter (as
allowed) where he/she will have a
relatively unobstructed view of the
developing fire. Use of the helitorch
can require 2 to 3 additional ground
support people to mix the fuel and
position the drums depending upon
torch configuration and company/
agency policy. Disposal of any unused
helitorch fuel mix can present additional
logistical problems; alumagel is toxic
and should never just be dumped.

Radios for communication are
essential for aerial ignition and for
any large burn. Behavior of a
prescribed burn will vary because of
roads or other openings in the timber
stand, varying fuel conditions, chang-
ing weather, and the firing technique
used. Two vehicles are essential to
permit maximum mobility of the
burning boss and crews. Chain saws
are useful additions to the equipment
The burning boss should have the
crew ready to fire the area as early in
the day as conditions permit, leaving

maximum time for mopup and patrol
of the lines. Normally, plan to com-
plete any one job within a standard
workday. The burning boss must
make sure the crew has the proper
clothing and safety equipment and is
in good physical shape. Proper
clothing includes long-sleeve fire
resistant or cotton shirts, pants
without cuffs, leather boots with non-
skid soles, safety glasses, hardhat,
gloves, and plenty of drinking water.
During the summer, the possibility of
heat exhaustion and heat stroke must
be considered.

Examples of prescribed burning equipment

Check fuel moisture of duff and litter

: :


1 '"
;'~r *I
F 'I,.

Post smoke warning signs

* Make sure all equipment is in
working order and safe to use.
* Carry burning plans and maps to
the job.
* Check the weather before starting
to burn and keep updated throughout
the day.
* Check all control lines, clean out
needles and leaves, and reinforce as
* Notify adjoining property owners
and local fire control organizations
before starting fire.

* Instruct crew on procedures, in-
cluding safety precautions and the
proper operation of equipment and
use of hand tools.
* Post signs on public roads and be
prepared to control traffic if potential
exists for smoke to reduce visibility.
* Check duff and soil for dampness.
* Test burn with a small fire before
firing; check the fire and smoke
behavior to make sure the fire is
burning as expected. If it is not,
decide whether the observed behavior
is acceptable. This is the time to

cancel the burn if you are not com-
fortable with the observed behavior.
* Inform crew of starting point and
firing sequence. Give each member a
* Have a means of instant com-
munication with all crew members.
Portable radios are very useful.
* Be alert to changing conditions,
and be prepared to change burning
techniques or plow the fire out if an
emergency arises.
* Burn so the wind will carry
smoke away from sensitive areas.
* Mopup and patrol perimeters con-
stantly during the operation, and
thereafter until there is no further
danger of fire escape or smoke

"Give Prescribed Burning
When Burning Weather Arrives"

Small test fire to check behavior of fire and smoke

Prompt mopup will minimize residual smoke

constantly monitor fire behavior

Evaluating the


The purposes of a burn evaluation
are to determine how well the stated
objectives of the burn were met and
to gain information to be used in
future burns. An initial evaluation
should be made immediately after the
burn, perhaps the following morning.
A second evaluation should be made
during or after the first postfire
growing season.

Points to be Considered
* Was preburn preparation properly
* Were objectives met?
* Was burning plan adhered to?
Were changes documented?
* Were weather conditions, fuel
conditions, fire behavior, and smoke
dispersion within planned limits?
* What were effects on soil, air,
vegetation, water, and wildlife?
* Was fire confined to intended
area; any escapes?
* Was burning technique correct?
* Were costs commensurate with
benefits derived?
* How can similar burns be

Indications and
Needle Scorch
The best indicator of crop tree
damage is percent foliage discolora-
tion. Assuming that buds and branch-
lets are not heat-killed, even crown
scorch approaching 100 percent
generally will not kill trees unless
secondary factors such as insect
attack or drought materialize. If,
however, loblolly pine stands are
burned in the fall (September or
October), after the trees have
undergone their last needle flush of
the growing season but prior to the
onset of dormancy, research indicates
that 100 percent crown scorch is like-
ly to kill them. Slash pine appears to
be more tolerant of severe crown
scorch during the fall.

If more than 15 percent of a southern
pine tree's needles are actually con-
sumed by flames, the tree's chances
of survival would be poor even if
very little of the rest of the crown is
scorched. Young vigorous trees are
more likely to survive severe crown
damage than are older individuals.
Magnitude and duration of growth
responses in southern pines due to
various levels and seasons of defolia-
tion are not well documented. Both
negative and positive responses have
been observed, but the preponderance
of evidence shows a direct relation-
ship between diameter and height
growth loss and crown scorch.
Providing no crown consumption
took place, the following table will
help in estimating potential growth
loss in loblolly and slash pines over
3 inches dbh. These "ball park"
estimates can be used for other
southern pines as well, until more
specific results become available.
A good indicator of hardwood
control is a series of bark cracks
extending into the cambium near ground
level. This indicates sufficient heat
was applied to penetrate the bark and
kill the cambium. Although large hard-
woods can be damaged by periodic
fires they are difficult to kill.
Judge the success of burning for
brownspot control by the number of
longleaf seedlings with all infected

needles burned off, but still having a
protective sheath of green needles
around the unharmed terminal bud.

Soil and Root Damage
Burning under prescribed conditions
in the South generally does not expose
bare soil. If duff remains after a
burn, the physical properties of the
soil probably were not harmed. If
mineral soil is exposed, especially on
steep slopes, soil movement and
deterioration of site quality may occur.
Root damage is likely whenever
the organic layer is completely con-
sumed. It should also be expected
whenever burns are conducted over
dry soils (drought conditions) or
when a deep litter layer is present,
even though some duff remains. New
root growth in vigorously growing
pines can usually offset these losses,
but older trees, having survived such
fires without crown damage, often die
six months to a year later for no
apparent reason.

Air Quality
Smoke behavior must be continually
evaluated from the time the fire is
ignited until smoldering ceases.
Unusual or unexpected smoke effects
should be noted and correlated with
other parameters of the burn for future
use. Any public complaints should be
recorded as part of the evaluation.

Percent Damage
Crown Scorch

0 to 33 Some volume growth loss may occur the first
postfire growing season but it will be minor.
34 to 66 Volume growth loss usually less than 40 percent
and confined to first postfire growing season.
67 to 100 Reduction may be as high as a full year's
volume growth spread over 3 years.

Timing and Points to
Evaluation should take place
immediately after the burn and again
during the first postfire growing
season. In the case of late summer
prescribed fires, the second evalua-
tion should take place the following
spring after the next growing season
has begun.

Points in First Evaluation
* Amount of overstory foliage
* Amount of consumption and top-
kill of understory vegetation.
* Consumption of infected needles
on longleaf seedlings without injury
to terminal bud.
* Amount of litter remaining on
forest floor.
* Smoke dispersion into upper
atmosphere and success in avoiding
smoke-sensitive areas.
* Protection of areas not to be
* Any escape of fire.
* Any adverse public comment or
reaction prior to, during, or
immediately after the burn.

Points in Future Evaluation
Future evaluation can best be
made after the start of the growing
season to determine the following:
* Resin exuding from pine trees, an
indicator of cambium damage or
insect attack.
* Other signs of beetle attack.
* Mortality of timber or other
desirable vegetation.
* Sprouting vigor of undesired
* Recovery of longleaf seedlings
free of brownspot.
* Remaining duff layer, mineral soil
exposed, and any soil movement.
* Public expression for or against
the burning program.

evaluating a prescnoea ourn

Coordination of


These guidelines are general and will not fit all situations.

REDUCE FUELS Winter Large enough to Not critical. Do 2 to 4 years Use line-backing fire, or point-
break fuel not ring fire. source fires under moist conditions
continuity for initial burn. Grid-firing techni-
que excellent for maintenance
IMPROVE General Protect transitional or
WILDLIFE fringe areas. Do not burn stream
HABITAT bottoms.
Deer Winter preferred Small or leave Backing fire or 2 to 4 years Want to promote sprouting and
unburned areas point-source fires keep browse within reach. Repeat
summer fires may kill some
Turkey Winter preferred; Small or leave Backing fire or 2 to 4 years Avoid April through June nesting
summer burns in unburned areas point-source fires season.
July August
Quail Late winter 25 + acres Not critical. Do 1 to 2 years Avoid April through June nesting
not ring fire season. Leave unburned patches
and thickets.
Dove Winter Not critical Not critical. Do Not critical Leave unburned patches and
not ring fire thickets.
Waterfowl Late fall or winter Not critical Heading fire 2+ years Marshland only. Do not burn in
hardwood swamps.
CONTROL Heavy roughs in Not critical. Not critical. Do 2 to 8 years Summer burns result in higher
COMPETING winter, otherwise not ring fire. rootstock kill and affect larger
VEGETATION not critical stems. Exclude fire from desirable
hardwoods in pine-hardwood type.

IMPROVE Winter through Not critical but Not critical. Do 3 years Split range and burn one-third
FORAGE FOR late spring for will be damaged not ring fire. each year. Individual herbs and
GRAZING most situations by overuse if too grasses respond differently to
small for herd. fire and season of burn. Consult
IMPROVE Will vary with Varies with in- Depends on As needed Coordinate with other resource ob-
ACCESSIBILITY understory and dividual situation amount of fuel jectives. They will dictate size, tim-
desired use present ing and frequency of burn.

CONTROL Brownspot, Depends on size Strip-heading or 2 to 3 years Burn when humidity is above 50%.
DISEASE winter of infected area. heading fire Avoid leaving unburned pockets of
Include a buffer infected seedlings within or adja-
strip cent to burn.


ENHANCE Late fall through Varies with each Backing fire or 1 + years Requires precise prescription to
APPEARANCE late winter situation point-source fire protect vegetative type changes.
Know effect of fire frequency and
season of burn on both annual and
biennial flowering plants. Provide
pleasing visual lines.

PERPETUATE Will vary with Will vary but Will vary with fuel Will vary with Fire intensity, timing and frequency
FIRE species usually fairly conditions and species all dictated by species
DEPENDENT small species requirements.
SPECIES requirements.

YOUNG PINE Winter Varies with size Backing fire 2 to 4 years Pine diameter 3 inches or more at
STANDS of stand ground. Pine height above 10 ft.
Burn only after a strong cold front
with rain.

DISPOSE OF Not critical Small areas Center firing with - Smoke management is a must
LOGGING mean fewer helitorch Take care not to damage soil or
DEBRIS nighttime smoke preferred water resources with these hot
problems fires. If a broadcast burn will not
meet objectives, pile do not wind-
row debris.

PREPARE SITES Natural seeding, Large enough to Not critical. Do Be careful not to kill seed trees. If
FOR SEEDING summer to early prevent concen- not ring fire logging debris present, manage
fall prior to seed trations of birds & your smoke.
fall. rodents (usually
10 acres or

Direct seeding, Large enough to Not critical. If logging debris present, smoke
fall to late winter prevent concen- Center firing with management is a must! Take care
for spring sowing. trations of birds & helitorch prefer- not to damage soil or water
Previous winter rodents (usually red if slash resources with these hot fires
for fall sowing of 10 acres or present.
longleaf. more).

PREPARE SITES Growing season Large enough to Not critical. If logging debris present, smoke
FOR PLANTING for hardwood prevent concen- Center firing with management is a must! Take care
control. trations of birds & helitorch pre- not to damage soil or water
rodents (usually ferred if slash resources with these hot fires
10 acres or present.

Rules of


1. Obtain and use latest weather and
smoke management forecasts.
2. Relative humidity will roughly
halve with each 200F rise in
temperature and double with each
200F drop in temperature in a
given air mass.
3. Expect increased spotting when
relative humidity drops below 30
percent. Do not burn when the
relative humidity is below 25
4. Burn when mixing height is
above 1,650 feet [500 meters].
5. Do not burn under temperature
6. Burn areas with low fuel loadings
and large-sized trees on marginal
days at the high end of the
prescription window.
7. Never underbur during a
drought. Soil moisture is needed
to protect tree roots and lower
8. Don't burn on organic soils unless
the water table is very close to
the surface.

9. Heading fires produce about three
times more particulate than back-
ing fires.
10. Burn when fuels are dry, but not
too dry. Wet fuels produce
substantially more particulate
than do dry fuels.
11. Start burning logging debris by
12. Site prep burning behind chop-
ping or other mechanical treat-
ment gives best results if done 10
to 15 days after treatment.
13. Windrows are the most polluting
of all southern fuel types.
14. Broadcast burn scattered debris if
15. Do not pile when either ground
or debris is wet.
16. Dirt in piled debris will increase
the amount of smoke produced by
up to four times. Shake out dirt
while piling; "bump" piles while
burning, and repile as necessary.
17. Use a smoke management plan.
Consider smoke sensitive areas.
Look several miles downwind and
down-drainage for potential

18. Estimate background smoke con-
centration [micrograms per cubic
meter] in the absence of high
humidities by dividing 500 by the
visibility in miles.
19. If nighttime Dispersion Index
forecast is poor or very poor
[less than 13], stop burning by
3 p.m. ST.
20. Doubling the Dispersion Index
implies a doubling of the atmos-
pheric capacity to disperse smoke
within a 1,000 square mile area.
21. Assuming 1 ton of fuel per acre
is being consumed by smoldering
combustion during poor nighttime
dispersion conditions, expect
visibility in the smoke to be less
than mile within 1% miles of
the fire.

Red Flag


If any of the following
conditions exist,
analyze further before
SNo written plan
No map
0 No safety briefing
0 Heavy fuels
Dry duff and soil
Extended drought
Inadequate control lines
No updated weather forecast
for area
N Forecast does not agree with
0 Poor visibility
E Personnel or equipment
stretched thin
Burning large area using
ground ignition
Communications for all people
not available
No backup plan or forces
No one notified of plans to

Behavior of test fire not as
A smoke-management system
has not been used
Smoke-sensitive area downwind
or down drainage
Organic soil present
Daytime Dispersion Index
below 40
Not enough personnel or
equipment available to control
an escaped fire
Personnel on fire not qualified
to take action on escaped fire.

Debris burning in addition to the
M Area contains windows
M A lot of dirt in piles
M Poor nighttime smoke disper-
sion forecast
M Have not looked down drainage
M Mixing height is below 1,650
feet (500 meters)
M Debris was piled when wet
M Pile exteriors are wet

If any of the following
conditions exist,
stop burning and plow
out existing fire.
Fire behavior erratic
Spot fire or slop-over occurs
and is difficult to control
Wind shifting or other unfore-
seen change in weather
Smoke not dispersing as
Public road or other sensitive
area smoked in
Bur does not comply with all
laws, regulations, and standards
Large fuels igniting and burn-
ing, not enough personnel to
mopup before dark and likely to
smoke in a smoke sensitive area


Aerial Fuels-Standing and sup-
ported live and dead forest com-
bustibles not in direct contact with
the ground consisting mainly of
foliage, twigs, branches, cones, bark,
stems, and vines (See Draped Fuels,
Ladder Fuels).
Aerial Ignition-Ignition of fuels by
dropping incendiary devices or
materials from aircraft.
Age of Rough-Time in years since
the forest floor was last reduced by
Air Stagnation Advisory (ASA) -
A statement issued by a National
Weather Service office when
atmospheric conditions are stable
enough that the potential exists for
pollutants to accumulate in a given
Anemometer-General name for
instruments designed to measure
Area Ignition-Igniting, throughout
an area to be burned, a number of
individual fires either simultaneously
or in rapid succession and so spaced
that they soon influence and support
each other to produce a hot, fast-
spreading fire throughout the area.
Aspect-Direction toward which a
slope faces.
Atmospheric Stability-A measure
of the degree to which the
atmosphere resists turbulence and
vertical motion. In prescribed fire
activities the atmosphere is usually
described as stable, neutral, or
Available Fuel-That portion of the
total fuel that would actually be
consumed under a specific set of
burning conditions.
Backing Fire-A fire spreading or
set to spread into (against) the wind,
or downhill. (See Flanking Fire,
Heading Fire).
BEHAVE -A system of interactive
computer programs for modeling fuel
and fire behavior comprised of two
subsystems: BURN and FUEL.

Belt Weather Kit-Belt mounted
canvas case with fitted pockets for
anemometer, compass, sling
psychrometer, slide rule, water bottle,
pencils, and book of weather report
Blackline-Preburning of fuels,
either adjacent to a control line
before igniting the main prescribed
fire, or along a roadway as a
deterrent to human-caused fires.
Blackline denotes a condition in
which there is no unburned fine fuel.
Broadcast Burn-Prescribed fire
that burns over a designated area,
generally in the absence of a
merchantable overstory, to consume
debris that has not been piled or
Brown & Burn-Application of
herbicide to desiccate living
vegetation prior to burning.
Brownspot Control-A prescribed
burn to control a fungal infection
(brownspot disease) of longleaf pine
in the "grass" (small seedling) stage.
Buildup-Cumulative effects of long-
term drying on current fire danger.
Buildup Index (BUI)-A relative
number expressing the cumulative
effect of daily drying factors and
precipitation on fuels with a 10-day
timelag constant.
Burning Boss-Person responsible
for managing a prescribed fire from
ignition through mopup.
Burning Index (BI)-A relative
number related to the contribution
fire behavior makes to the amount of
effort needed to contain a fire within
a given fuel type. A doubling of the
BI indicates twice the effort will be
needed to contain a fire in that fuel
type as was previously required.
Category Day-A numerical index
related to the ability of the atmos-
phere to disperse smoke. For
example, in South Carolina the
current scale, based on Ventilation
Factor, ranges from 1 (poor) to 5

Catface-Defect on the surface of a
tree resulting from a wound where
healing has not re-established the
normal cross-section.
Center Firing-A method of
broadcast burning in which fire(s) are
set in the center of the area to create
a convection column with strong
surface indrafts. Usually additional
fires are then set progressively nearer
the outer control lines as the indraft
builds up, to draw the flames and
smoke toward the center of the burn.
Chain -Unit of measure in land
survey equal to 66 feet; 80 chains
equal 1 mile.
Clearcutting-Removal of the entire
standing, merchantable timber crop.
Cold Front-The leading edge of a
mass of air that is colder and drier
than the air mass being replaced.
Control Line-Comprehensive term
for all constructed or natural fire
barriers and treated fire edges used to
control a fire.
Convection Column-The rising
column of gases, smoke and debris
produced by a fire. The column has a
strong vertical component indicating
that buoyant forces override the
ambient surface wind (See Smoke
Convergence Zone-The area of
increased flame heights and fire
intensity produced when two or more
flame fronts burn together.
Crown Scorch-Browning of needles
or leaves in the crown of a tree or
shrub caused by heat from a fire.
Cured-Debris or herbaceous
vegetation that has dried and lost its
green color.
DAID (Delayed Aerial Ignition
Device)- See Ping-pong Ball
Debris Burning-In this publication,
defined as any prescribed fire used to
dispose of scattered, piled, or
windrowed dead woody fuel in the
absence of an overstory. Such a burn
often accomplishes the objectives of a
Site Prep Burn as well.

Dew Point-Temperature to which air
must be cooled to reach saturation at
a constant atmospheric pressure. The
dew point is always lower than the
wet-bulb temperature, which in turn
is always lower than the dry-bulb
temperature. The only exception to
this is when the air is saturated (i.e.,
relative humidity is 100 percent), in
which case all three values are equal.
Dispersion-The decrease in
concentration of airborne pollutants
as they spread throughout an
increasing volume of atmosphere.
Dispersion Index-As used in this
manual, a numerical index developed
by Lee Lavdas (Southern Forest Fire
Laboratory). This index is an
estimate of the atmosphere's capacity
to disperse smoke from prescribed
burns over a 1,000-square-mile area.
It is related to the Ventilation Factor,
but also considers the rate of
pollutant dispersion.
Draped Fuels-Needles, leaves,
twigs, etc., that have fallen from
above and have lodged on lower
branches and brush. Part of aerial
Drift Smoke-Smoke that has been
transported from its point of origin
and in which convective motion no
longer dominates.
Drip Torch-Hand-held apparatus
used to ignite fires by dripping
flaming liquid fuel, at an adjustable
rate, on the materials to be burned.
The fuel is generally a mixture of 65
to 80 percent diesel and 20 to 35
percent gasoline.
Drought Index (Keetch-Byram
Drought Index)-A numerical rating
of the net effect of evapotranspiration
and precipitation in producing
cumulative moisture depletion in
deep duff or upper soil layers.
Dry-bulb Temperature-The
temperature of the air.

Duff-The layer of decomposing
organic materials lying below the
litter layer and immediately above the
mineral soil. It is comprised of the
Fermentation (F) and Humus.(H)
layers of the forest floor.
Edge-As used in this manual, the
boundary between two fairly distinct
fuel types.
Emission Factor-The amount of
pollution (pounds per ton) released to
the atmosphere per unit weight of dry
fuel consumed during combustion.
Emission Rate-The quantity of
pollutant released to the atmosphere
per unit length of fire front per unit
Equilibrium Moisture Content
(EMC)-The moisture content that a
fuel would eventually attain if
exposed for an infinite period to
specified constant values of Dry-bulb
Temperature and Relative Humidity.
Fine Fuels (Flash fuels)-Fast-
drying, dead fuels which have a
Timelag constant of 1 hour or less.
These fuels ignite readily and are
consumed rapidly when dry. Included
are grass, leaves, draped pine
needles, and small twigs.
Fire Behavior-A general term that
refers to the combined effect of fuel,
weather and topography on a fire.
Firebrand-Any flaming or
smoldering material such as leaves,
pine cones, or glowing charcoal that
could start another fire.
Firebreak-Any natural or
constructed discontinuity in a fuelbed
used to segregate, stop, or control the
spread of fire or to provide a control
line from which to suppress a fire.
Fire Effects-Physical, biological
and ecological impacts of fire on the
Fire Front-The strip within which
continuous flaming occurs along the
fire perimeter (See Flame Depth).

Fireline Intensity (Byram's
Intensity)- The rate of heat release
per unit time per unit length of fire
front. Numerically, it is the product
of the heat yield, the quantity of fuel
consumed in the Fire Front, and the
rate of spread.
Fire Plow-Heavy-duty share or disk
plow designed to be pulled by a
tractor to construct Firebreaks.
Fire Rake-A long-handled
combination rake and cutting tool,
the blade of which is usually
constructed of a single row of 4
sharpened teeth.
Firing Technique-The type(s) of
fire resulting from one or more
ignition(s), e.g., backing fire,
flanking fire, heading fire, (See Grid
Ignition, Ignition Pattern).
Flame Depth-The depth of the Fire
Front at the fuel surface.
Flame Length-The distance between
the flame tip and the midpoint of the
Flame Depth at the base of the flame
(generally at the ground surface).
Flanking Fire-A Fire Front
spreading, or set to spread at roughly
right angles to the prevailing wind.
Flash Fuels-See Fine Fuels.
Flying Drip Torch-See Helitorch.
Fuel Moisture Content-Water
content of a fuel expressed as a
percentage of the ovendry weight of
the fuel.
Fuel Moisture Indicator Sticks-A
specially manufactured set of sticks
of known dry weight continuously
exposed to the weather and
periodically weighed to determine
changes in moisture content. The
changes are an indication of changes
in the moisture status and relative
flammability of dead fuels that
roughly correspond toTen-hour
Timelag Fuels.
Grid Ignitions-Method of igniting
fires in which ignition points are set
individually at predetermined spacing
with predetermined timing throughout
the area to be burned (see Ping-pong
Ball System).

Hazard Reduction-Treatment of
living and dead forest fuels to reduce
the likelihood of a fire starting, and
to lessen its damage potential and
resistance to control.
Heading Fire-A Fire Front
spreading or set to spread with the
wind or upslope.
Helitorch (Flying Drip Torch)-A
specialized drip torch hung from, or
mounted on a helicopter that
dispenses globs of ignited gelled
Herbaceous Fuels-Grasses and
other plants that contain little woody
Humus-The layer of decomposed
organic matter on the forest floor
beneath the partially decomposed
litter layer (F layer) and directly
above the soil.
Hygrothermograph-An instrument
that continuously records Dry-bulb
Temperature and Relative Humidity.
Ignition Pattern-The manner in
which a Prescribed Fire is ignited.
The distance between ignition lines
or points and the sequence of igniting
them, as determined by fuel, topo-
graphy, weather, ignition system,
firing technique, and other factors
influencing fire behavior and the
objectives of the burn (See Firing
In-stand Wind (Midflame Wind)-
Windspeed within a stand at about
eye level.
Inversion-In this publication,
defined as a layer of the atmosphere
through which the temperature
increases with increasing height.

Keetch-Byram Drought Index-See
Drought Index.
Ladder Fuels Fuels that provide
vertical continuity between the ground
and tree crowns, thus creating a
pathway for a surface fire to move into
the overstory tree crowns.

Line Ignition-Setting a line of fire
as opposed to individual spots.
Litter-The top layer (L layer) of the
forest floor directly above the
fermentation layer (F layer),
composed mainly of recently fallen
leaves and pine needles, but also
includes dead twigs, bark fragments,
etc. (See Duff).
Logging Debris-Unwanted tree
parts remaining after harvest,
including tree crowns, unutilized
logs, and uprooted stumps.
Low-Level Jet-See Wind Profile.
Midflame Wind-See In-stand wind.
Mineral Soil-Soil layers below the
predominantly organic horizons.
Mixing Height-The height to which
relatively vigorous mixing of the
atmosphere occurs.
Mopup-Extinguishing or removing
burning material, especially near
control lines after an area has burned
to make it safe, or to reduce residual
Muck-See Organic Soil.
National Fire Danger Rating
System (NFDRS)-The method
currently used by the USDA Forest
Service, and many other
organizations to integrate the effects
of topography, fuels, and weather into
numerical indices of fire danger on a
day-to-day basis.
One-Hour Timelag Fuels-Fine
fuels consisting mainly of dead
herbaceous plants, roundwood less
than about 14-inch in diameter, and
the uppermost Litter Layer.
Organic Soil-Any soil or soil
horizon containing at least 30 percent
organic matter; examples are peat
and muck.
Particulate (Total Suspended
Particulate (TSP))-Any liquid or
solid particles temporarily suspended
in the atmosphere. See PM-10.
Peat-See Organic Soil.

Ping-pong Ball System-A method
of igniting fires with the use of a
Delayed Aerial Ignition Device
(DAID). The device is a polystyrene
ball, 1.25 inches in diameter that
contains a combustible chemical. The
balls are fed into a dispenser,
generally mounted in a helicopter,
where they are injected with another
chemical and drop through a chute
leading out of the helicopter. The
chemicals react thermally and ignite
in about 30 seconds. The space
between ignition points on the ground
is primarily a function of helicopter
speed, gear ratio of the dispenser,
and the number of chutes used (up to
4) (See Grid Ignition).
PM-10-Particulate with an aero-
dynamic diameter smaller than or
equal to 10 micrometers.
Prescribed Burning-The controlled
application of fire to wildland fuels
in either a natural or modified state,
under specified environmental
conditions which allow the fire to be
confined to a predetermined area and
at the same time produce the
intensity required to attain planned
resource management objectives.
Psychrometer-The general name for
instruments designed to determine the
moisture content of air. A psychro-
meter consists of dry-and wet-bulb
thermometers that give the Dry-and
Wet-bulb Temperatures, which in turn
are used to determine Relative
Humidity and Dew Point.
Relative Humidity-The ratio,
expressed as a percentage of the
amount of moisture in the air, to the
maximum amount of moisture the air
is capable of holding under the same
Residence Time-The time (seconds)
required for the Fire Front to pass a
stationary point at the surface of the
fuel. Numerically, it is the Flame
Depth divided by the rate of spread.
Residual Smoke-Smoke produced
by smoldering material behind the
actively burning Fire Front.

Ring Fire-A fire started by igniting
the perimeter of the intended burn
area so that the ensuing Fire Fronts
converge toward the center of the
Rough-The live understory and dead
fuels that build up on the forest floor
over time.
Scorch Height (Scorch Line)-The
average height to which foliage has
been browned by fire.
Site Prep Burn-A fire set to expose
adequate mineral soil and control
competing vegetation until seedings
of the desired species become
established (See Debris Burning).
Slash-Debris resulting from such
natural events as wind, fire, or snow
breakage, or such human activities as
logging or road construction .
Smoke Concentration-The weight
of combustion products (micrograms
per cubic meter) found in a given
volume of air.
Smoke Management-Application of
knowledge of fire behavior and
meteorological processes to minimize
air quality degradation during
Prescribed Burning.
Smoke Plume-The gases, smoke,
and debris that rise slowly from a
fire while being carried along the
ground because the buoyant forces
are exceeded by those of the ambient
surface wind (See Convection
Smoke-sensitive Area (SSA)-An
area in which smoke from outside
sources is intolerable.
Smoldering Combustion Phase-
Combustion associated with residual
burning of forest fuels behind the
Fire Front. Emissions are at least
twice that of the Fire Front, and
consist mainly of tars.
Spot Fire-Fire ignited outside the
perimeter of the main fire by a Fire

Spot Weather Forecast-Special
prediction of atmospheric conditions
at a specific site, sometimes requested
by the Burning Boss before igniting a
prescribed fire.
Stagnant Conditions-Conditions
under which pollutants build up faster
than the atmosphere can disperse
Strip-Heading Fire-A series of
lines of fire upwind (or downslope)
of a firebreak or backing fire that
will burn with the wind toward the
firebreak or backing fire.
Ten-Hour Timelag Fuels-Dead
roundwood A4 to 1 inch in diameter
and, to a rough approximation, the
top inch of the litter layer.
Timelag-The drying time, under
specified conditions, required for a
dead fuel to loose about 63 percent
of the difference between its initial
moisture content and its Equilibrum
Moisture Content. Providing
conditions remain unchanged, a fuel
will reach 95 percent of its EMC
after four timelag periods.
Tractor-Plow-Any tracked vehicle,
with a plow for exposing mineral
soil, with transportation and
personnel for its operation.
Transport Windspeed-A measure
of the average rate of the horizontal
movement of air throughout the
mixing layer.
Underburning-Prescribed burning
under a timber canopy.
Ventilation Factor-An indicator of
the lower atmosphere's potential to
diffuse and disperse smoke.
Numerically, it is the product of the
Mixing Height and the Transport
Windspeed (See Dispersion Index).
Wet-bulb Temperature-Technically,
the temperature registered by the wet-
bulb thermometer of a Psychrometer.
It is the lowest temperature to which
air can be cooled by evaporating
water into it at a constant atmos-
pheric pressure.

Wetline-A line of water, or water
and chemical retardant, sprayed along
the ground and which serves as a
temporary control line from which to
ignite or stop a low-intensity fire.

Wind Direction-Compass direction
from which the wind is blowing.
Wind Profile-A plot of windspeed
over height above the earth's surface.
A rapid increase with height to a
maximum windspeed within 1,000
feet above ground and then a slow
decrease above that peak is commonly
called a low-level jet and is one of
several adverse wind profiles.
Windrow-Woody debris that has
been piled into a long continuous





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For information about articles,
contact: USDA Forest Service,
Southern Region, Fire and Aviation
Staff Unit, 1720 Peachtree Road NW,
Atlanta, GA 30367 or USDA Forest
Service, Southeastern Forest
Experiment Station, P.O. Box 2680,
Asheville, NC 28802

I i-3:$Ir!

Five Steps to a Successful
Prescribed Burn

Dote Due

3 1262 04248 54140




The Forest Service, U.S. Department of Agriculture, is responsible I-or Federal
leadership in forestry. It carries out this role through four ruaiu activitic:
0 Protection and management ofresources on 191 million acres of National Forest
System lands.

I,005T 5ERVq Cooperation With State and local governments, forest industries, and pt ivate
landowner to help protect and manage non-Fedcral lorest WId associated range
an(] watershed land,,,.
b* S 'Participation with other agencies in hurnan resource Wid COMIMIT11t%, asjqatw,,
IWOF programs to improve living conditions in rural areas.
Research on all aspects ot'lorcstry, rangeland management, and lorest resources

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