A. M. Pettis
Agricultural Extension Service
Institute of Food and Agricultural Sciences
University of Florida, Gainesville
PORTABLE FIRE EXTINGUISHERS
A. M. Pettis
Extension Safety Leader
The subject of portable fire extinguishers is
confusing to many people. This is probably due
to misinformation or lack of information regard-
ing the various types of extinguishers available.
A portable fire extinguisher contains a limited
supply of some fire extinguishing agent. Some
extinguishers are suitable for use on only one
kind (class) of fire and this equipment would
probably be ineffective and may even be danger-
ous if used on other classes of fire.
How are fires extinguished? To answer this
question one should consider the three components
necessary to have a fire, as shown below in the
In order to have a fire, heat (not a flame), air
(or oxygen), and fuel are necessary. If one of
these components is absent, there can be no fire.
For example when firemen put a stream of water
on a burning object, the water cools the burning
material below the temperature necessary for
combustion and the fire is extinguished. See Table
2 for explanation of how different kinds of fires
There are three common kinds (classes) of fires
and any of these may occur in or around homes.
It is important for a person who attempts to
extinguish a fire to know what kind of fire he is
combating and the type extinguisher that should
be used. In different locations, within the home,
certain kinds of fires are most likely to occur.
This information is necessary in setting up an
adequate fire protection system. (See Table 1)
TABLE 1.-Classes of Fires and Recommended Extinguishers
Class Involves Extinguisher Recommended
A Wood, paper, textiles, Pressurized water
trash, grass, etc. ABC all-purpose pres-
surized Water pump
Garden hose & nozzle
B Gasoline, kerosene, ABC all-purpose
greases, oils, paints, pressurized
C Electrical CO0
IMPORTANT: All extinguishers should have the U. L. approval label.
TABLE 2.-How Different Classes of Fires are Extinguished
Class A Extinguished by cooling or excluding the
heat from the fire.
Class B Extinguished by smothering or excluding
Class C Extinguished by excluding oxygen. The
electricity must be turned off or the ex-
tinguishing agent will be of no help since
the current continues to flow. Also of
great importance is the fact that water
is a conductor of electricity and should
never be used for control of Class C fires.
Where more than one extinguisher is listed for
a class of fire, the first one on the list is the pre-
ferred choice. These extinguishers are recom-
mended for homes because they have certain
Pressurized Water.-(21/2 gallon with pressure
gauge) Advantages Can be used on fire inter-
mittently as desired. A glance at the gauge and
you know it is ready for use. The homeowner can
refill easily by adding water, closing lid, and
applying the correct air pressure (compressed
air is available at service stations, fire stations,
etc.). Note-a wetting agent such as ordinary
detergent (1 ounce per gallon) should be added.
This breaks down surface tension of the water
and results in better performance. Disadvan-
tage-It must be protected against freezing.
ABC all-purpose pressurized- (21/2 pounds or
41/2 pounds with gauge)-This extinguisher con-
tains a special chemical and it is effective on
Classes A, B and C fires. It can be used intermit-
tently as desired. The pressure gauge serves as
an indicator to show the extinguisher is ready
for use or needs recharging.
Pressurized dry chemical,- (23/% pounds or 4
pounds with gauge)-Advantage The active
chemical is ordinary baking soda, which will not
harm humans or fabrics. This extinguisher may
be operated in a similar manner to the ABC all-
purpose pressurized extinguisher but it is not
effective on Class A fires.
IMPORTANT: It is extremely important to read
the instructions for using all pressurized type
extinguishers. Some people who have had ex-
perience in the use of the soda-acid type try to
use the pressurized type in the same manner, thus
discharging only the pressure.
CO2 (carbon dioxide).-Advantage Especial-
ly good on electrical fires because it leaves no
residue. Disadvantages It must be weighed to
determine when a recharge is needed. Sometimes
a leaky valve may result in an extinguisher being
empty when it is needed. Be careful not to direct
this extinguisher toward a person because of the
extreme cold (temperature far below zero Fah-
renheit) produced by the compressed carbon di-
oxide gas. This extinguisher would be less effec-
tive on open porches or out of doors because of air
There are other types of approved extinguish-
ers available. Some are excellent in special loca-
tions when used by trained personnel, but are not
recommended for homes. Here are some common
extinguishers that are not recommended for home
use because of the reasons given:
Soda-Acid.-The acid could burn or blind people,
and it will damage fabrics, etc. Once inverted,
the extinguisher cannot be stopped until complete-
Foam.-A skilled operator is needed for satis-
Vaporizing Liquid.-The chemical used is car-
bon tetrachloride, chlorobromomethane, or a simi-
lar chemical. When this liquid is vaporized by
the heat of the flame, extremely toxic or deadly
fumes may be given off.
Gas Cartridge.-Once the cartridge has oper-
ated, the extinguisher must be completely dis-
charged. Malfunctions are more likely to occur
with this type extinguisher than with some other
Salt Shaker Type.-This type is not approved
by the National Board of Fire Underwriters. The
user could not get close enough to a hot fire to
Examples of dry chemical extinguishers.
Summary.-There are new types of portable
fire extinguishers (such as the pressurized ex-
tinguishers with pressure gauge) that have been
developed in recent years. These are far more
effective, easier and safer to operate, and easier
and cheaper to maintain than older types, par-
ticularly the soda-acid type.
Some of the older types may have a lower first
cost than the new types but often an additional
annual cost of recharging and inspection by a
qualified serviceman is required.
Portable extinguishers of the proper type,
readily available, can be extremely valuable in
extinguishing fires in their early stages. The
homeowner should determine the most likely lo-
cation for fires, the kind of fire most likely to
occur and the type or types of extinguishers
needed to combat them.
If a home has only one extinguisher, an ABC
all-purpose pressurized extinguisher would be
most valuable. This type or a pressurized dry
chemical extinguisher would also be useful in the
automobile and mounted on the tractor. If a
second extinguisher is obtained for the home, it
should be a pressurized water type for use on
Class A fires.
The fire extinguishers recommended for the
home in this publication may be obtained in
larger sizes than listed, if desired.
COOPERATIVE EXTENSION WORK IN
AGRICULTURE AND HOME ECONOMICS
(Acts of May 8 and June 30, 1914)
Agricultural Extension Service, University of Florida
United States Department of Agriculture, Cooperating
M. O. Watkins. Director