A Brief Introduction to Fire Extinguishers and Fire Types

When used properly, portable fire extinguishers can save lives and property by putting out a small fire or containing it until the fire department arrives.

Portable fire extinguishers for home use, however, are not designed to fight large or spreading fires. Even for small fires they are useful only under certain conditions:

  • The operator must know how to use the extinguisher. There is no time to read directions during an emergency.
  • The extinguisher must be within easy reach and in working order, fully charged.
  • The operator must have a clear escape route that will not be blocked by fire.
  • The extinguisher must match the type of fire being fought. Extinguishers that contain water are unsuitable for use of grease and electrical fires.
  • The extinguisher must be large enough to put out the fire. Many portable extinguishers discharge completely in as few as 8 to 10 seconds.

What Type of Extinguisher Should I Use?
There are three basic classes of fires, and all extinguishers are labeled as to what type of fire they can put out. They will have standard symbols on them and if there is a red slash through a symbol that tells you it cannot be used on that kind of fire.

The fire extinguisher must be appropriate for the type of fire being fought. If you use the wrong kind of fire extinguisher, you can make the fire worse and endanger yourself (for example, if you use a water extinguisher on an electrical fire, you'll find that to be quite a shocking experience ... using a pressurized extinguishing agent on a grease fire will spread the fire rather than extinguishing it). Multipurpose fire extinguishers can be used on all three classes of fires.

Class A

Ordinary Combustibles

Extinguish ordinary combustibles by cooling the material below its ignition temperature and soaking the fibers to prevent re-ignition. Use pressurized water, foam or multipurpose (ABC-rated) dry chemical extinguishers.

DO NOT USE carbon dioxide or ordinary (BC-rated) dry chemical extinguishers on Class A fires.
Class B

Flammable Liquids, Greases, or Gases

Extinguish flammable liquids, greases or gases by removing the oxygen, preventing the vapors from reaching the ignition source or inhibiting the chemical chain reaction.

Foam, carbon dioxide, ordinary (BC-rated) dry chemical, multipurpose dry chemical, and halon extinguishers may be used to fight Class B fires.
Class C

Energized Electrical Equipment

Extinguish energized electrical equipment by using an extinguishing agent that is not capable of conducting electrical currents.

Carbon dioxide, ordinary (BC-rated) dry chemical, multipurpose dry chemical and halon fire extinguishers may be used to fight Class C fires.

DO NOT USE water extinguishers on energized electrical equipment.

What Size Extinguisher Should I Buy?
Portable fire extinguishers are also rated for the size of fire they can handle. This rating will appear on the label - for example, 2A:10B:C. The larger the numbers, the larger the fire that the extinguisher can put out ... but the higher-rated models are often much heavier. Make sure you can hold and operate an extinguisher before you buy it.

What You Need to Know About Installing and Maintaining Extinguishers

  • Fire extinguishers should be installed in plain view, above the reach of children, near an escape route and away from stoves and heating appliances.
  • Fire extinguishers require some routine care. Make sure you read your operator's manual to learn how to inspect your fire extinguisher. Follow the manufacturer's instructions on maintaining the extinguisher.
  • Rechargeable models must be serviced after every use (look in the Yellow Pages of your telephone directory under "Fire Extinguishers" for local companies that service them). The disposable fire extinguishers can be used only one time and must be replaced after use.

How To Use Portable Fire Extinguishers

Remember the PASS system:
P...Pull the Pin
A...Aim extinguisher nozzle at the base of the flames
S...Squeeze trigger while holding the extinguisher upright
S...Sweep the extinguisher from side to side

ALWAYS make sure the fire department is called and inspects the fire site, even if you think you have extinguished the fire!

Should You Try to Fight the Fire?
Before you begin to fight a fire:

  • Make sure everyone has left or is leaving the building
  • Make sure the fire department has been called
  • Make sure the fire is confined to a small area and is not spreading
  • Make sure you have an unobstructed escape route to which the fire will not spread
  • Make sure you have read the instructions and know how to use the extinguisher
  • It is reckless to fight a fire in any other circumstances. Instead, leave immediately and close off the area.