Fire extinguishers are labeled according to the type of fire on which they may be used. Fires involving wood or cloth, flammable liquids, electrical, or metal sources react differently to extinguishers. Using one type of extinguisher on the wrong type of fire could be dangerous and make matters even worse.
Traditionally, the labels A, B, C, or D have been used to indicate the type of fire on which an extinguisher is to be used.
Class A Extinguishers will put out fires in ordinary combustibles, such as wood, paper, rubber, and many plastics. 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.
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.
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.
Class D Extinguishers are designed for use on flammable metals such as magnesium , titanium and sodium. These types of fire are very dangerous and seldom handled by the general public. These extinguishers generally have no rating nor are they given a multi-purpose rating for use on other types of fires.
Fire extinguishers also have a number rating. For Type A fires, a 1 would stand for 1 1/4 gallons of water, a 2 would represent 2 1/2 gallons, 3 would be 3 3/4 gallons of water, etc. For Type B and Type C fire, the number represents square feet. For example, 2 would be two square feet, 5 is five square feet, etc.
Fire extinguishers can also be made to extinguish more than one type of fire. For example, you might have an extinguisher with a label that reads 2A5B. This would mean this extinguisher is good for Type A fires with a 2 1/2 gallon equivalence and it is also good for Type B fires with a 5 square feet equivalency.
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
Pull the pin at the top of the extinguisher that keeps the handle from being accidentally pressed.
Aim the nozzle toward the base of the fire.
Stand approximately 8 feet away from the fire and squeeze the handle to discharge the extinguisher. If you release the handle, the discharge will stop.
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!