Fire Extinguishers – Classifications

Extinguishers and Fire Classifications

Fires and extinguishers are classified according to the type of fuel that is being consumed by the fire.

Classes of Fires

Types of Fires

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A

Wood, paper, cloth, trash and other ordinary materials

B

Gasoline, oil, paint and other flammable liquids

C

May be uised on fires involving live electrical equipment without danger to the operator

D

Combustible metals and combustible metal alloys

K

Cooking media (vegetable or animal oils and fats)

 

Types of Fire Extinguishers

No fire extinguisher can be safely and effectively used for every type of fire. Some contain chemicals that are ineffective in certain situations and can even cause harm to the operator if misapplied. To prevent confusion, extinguishers are classified by the type of chemical agents they contain. Generally, you can tell which type an extinguisher is hanging on the wall, or in the cabinet, just by looking at its shape. Check the labels of the extinguishers in your area and note the color, shape, and size of the extinguisher. This may help if someone runs in to help you fight a fire with the WRONG extinguisher (i.e. water on an electrical fire) - you can STOP them before they are injured or make matters worse!

 

ABC-Rated Multipurpose Dry Powder Extinguishers

  • Description: There are two types of fire extinguishers that use a dry chemical. One is called “multi-purpose dry chemical” and is effective on “A,” “B,” and “C” class fires. These types of extinguishers are very common and are found in schools, homes, hospitals and offices. The other type is known as “regular dry chemical,” capable of handling “B” and “C” class fires. These extinguishers are found in garages, kitchens and laboratories.
  • Appearance: These are the most common on campus, particularly in the corridors of academic buildings. They are almost always RED in color and have either a long narrow hose or no hose (just a short nozzle). These extinguishers are very light (5-25 lbs total weight).

 

Carbon Dioxide

  • Description: These extinguishers contain liquid CO2 that is expelled as a gas. They are effective against “B” and “C” class fires. Unlike other chemicals, CO2 does not leave a harmful residue and is environmentally friendly. It also poses very little danger to electronics and is effectively employed in laboratories, computer rooms, and other areas with sensitive equipment.
  • Appearance: CO2 (carbon dioxide) extinguishers are generally red, have a LARGE "tapered" nozzle (horn), are VERY HEAVY (15-85 lbs.) These are all high-pressure cylinders.

 

Water Extinguishers

  • Description: These extinguishers are most suited for “A” class fires. However, they cannot be used in “B,” “C” or "D" class fires. In "B" and "D" class fires, the water will spread the flames. In a "C" class fire, the water is conductive and poses a risk of electric shock to the operator. However, the misting nozzle of a "Water Mist" extinguisher breaks up the stream of deionized water so that there is no conductive path back to the operator. Since the agent used is water, these types of extinguishers are inexpensive and environmentally friendly.
  • Appearance: Water extinguishers are usually SILVER (crome-metal) in color, have a flat bottom, have a long narrow hose, and are quite large (2-1/2 gallons).

 

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