All You Ever Wanted to Know About . . .
Fire Extinguishers
There are basically four different types or classes of fire extinguishers, each of which extinguishes
specific types of fire. Newer fire extinguishers use a picture/labeling system to designate which types
of fires they are to be used on. Older fire extinguishers are labeled with colored geometrical shapes
with letter designations. Both of these types of labels are shown below with the description of the
different classes of extinguishers.
Additionally, Class A and Class B fire extinguishers have a numerical rating which is based on tests
conducted by Underwriter’s Laboratories that are designed to determine the extinguishing potential
for each size and type of extinguisher. Click on any of the topics listed below for additional
information that may be helpful to know.
Fire Extinguisher Ratings
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Class A Extinguishers will put out fires in ordinary
combustibles, such as wood and paper. The numerical rating for this class of fire extinguisher
refers to the amount of water the fire extinguisher holds and the amount of fire it will
extinguish. |
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Class B Extinguishers should be used on fires involving
flammable liquids, such as grease, gasoline, oil, etc. The numerical rating for this class of fire
extinguisher states the approximate number of square feet of a flammable liquid fire that a non-expert
person can expect to extinguish. |
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Class C Extinguishers are suitable for use on
electrically energized fires. This class of fire extinguishers does not have a numerical rating. The
presence of the letter “C” indicates that the extinguishing agent is non-conductive. |
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Class D Extinguishers are designed for use on flammable metals
and are often specific for the type of metal in question. There is no picture designator for Class D
extinguishers. These extinguishers generally have no rating nor are they given a multi-purpose
rating for use on other types of fires. |
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Multi-Class Ratings
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Many extinguishers available today can be used on different types of fires and will be labeled with
more than one designator, e.g. A-B, B-C, or A-B-C. Make sure that if you have a multi-purpose
extinguisher it is properly labeled.
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| This is the old style of labeling indicating suitability for use on Class A, B, and C fires. |
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This is the new style of labeling that shows this extinguisher may be used on Ordinary Combustibles,
Flammable Liquids, or Electrical Equipment fires. This is the new labeling style with a diagonal red
line drawn through the picture to indicate what type of fire this extinguisher is NOT
suitable for. In this example, the fire extinguisher could be used on Ordinary Combustibles and
Flammable Liquids fires, but not for Electrical Equipment fires. |
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Types of Fire Extinguishers
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Dry Chemical extinguishers are usually rated for multiple purpose use. They contain an extinguishing agent and use a compressed, non-flammable gas as a propellant.
Halon extinguishers contain a gas that interrupts the chemical reaction that takes place when fuels burn. These types of extinguishers are often used to protect valuable electrical equipment since them leave no residue to clean up. Halon extinguishers have a limited range, usually 4 to 6 feet. The initial application of Halon should be made at the base of the fire, even after the flames have been extinguished.
Water These extinguishers contain water\ and compressed gas and should only be used on Class A (ordinary combustibles)fires.
Carbon Dioxide (CO2) extinguishers are most effective on Class B and C (liquids and electrical) fires. Since the gas disperses quickly, these extinguishers are only effective from 3 to 8 feet. The carbon dioxide is stored as a compressed liquid in the
extinguisher; as it expands, it cools the surrounding air. The cooling will often cause ice to form around the “horn” where the gas is expelled from the extinguisher. Since the fire could re-ignite, continue to apply the agent even after the fire appears to be out.
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How to Use a Fire Extinguisher
Even though extinguishers come in a number of shapes and sizes, they all operate in a similar
manner.
Here's an easy acronym for fire extinguisher use:
P A S S -- Pull, Aim, Squeeze and Sweep
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| Pull the pin at the top of the extinguisher that keeps the handle from being accidentally pressed.
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| Aim the nozzle toward the base of the fire. Stand approximately 8 feet away from the fire.
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| Squeeze the handle to discharge the extinguisher. If you release the handle, the discharge will stop.
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| Sweep the nozzle back and forth at the base of the fire. After the fire appears to be out, watch it carefully since it may re-ignite!
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| Congratulations -- you did it!!!
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