Types of Fire Extinguishers

Fire extinguishers are useful tools that can be used to stop small fires from spreading and possibly becoming larger. They can be found in businesses, homes, offices, and vehicles that carry flammable goods. The National Fire Protection Association (NFPA) has established standards for the use of fire extinguishers in buildings and other structures. These standards require that fire extinguishers be inspected and serviced at least once every 30 days by a qualified technician. A fire extinguisher that is not inspected or serviced regularly will lose its pressure, and this can make it impossible to use.

The types of fires that can be extinguished by an extinguisher are divided into classes. A class A fire involves organic solids, such as wood and paper; a class B fire is a flammable liquid, such as gasoline or paint thinner; a class C fire occurs in electrical equipment, such as computers or appliances; and a class D fire concerns combustible metals, such as sodium and magnesium.

Different fire extinguishers are used to combat each of these types of fires. Water is typically used for class A fires, and carbon dioxide is usually employed for class B and C fires. Other common types of fire extinguishers include dry chemicals, wet chemicals, and halon.

A dry chemical (such as monoammonium phosphate) or wet chemical extinguisher (potassium acetate or potassium carbonate) works by creating an air-excluding soapy foam that smothers the flames. The chemical also cools the oil burning inside the fire, preventing it from reaching its ignition temperature. A standard stored-pressure ABC dry chemical extinguisher looks like a yellow talcum powder with nitrogen gas for propellant and can have a range of about 15 feet.

Halon fire extinguishers contain bromochlorodifluoromethane, or halon 1211, as their extinguishing agent. This type of fire extinguisher is effective for class B and class C fires because it does not conduct electricity. It works like an ABC extinguisher and requires that the user pull the pin, aim low at the base of the fire, sweep from side to side, and squeeze the handle.

Some home improvement stores sell multipurpose fire extinguishers, which can be used on class A, class B, or class C fires. These are a convenient alternative to buying separate B and C fire extinguishers.

A liquefied carbon dioxide fire extinguisher releases a cloud of pressurized CO2 that smothers the fire. It is most often used on class B and class C fires, although it may be effective on class A fires if they are not too large. Liquid carbon dioxide has very little range, but it is very effective at smothering fires and reducing their heat. Carbon dioxide is a non-toxic and environmentally friendly fire extinguisher, making it preferred in many areas of the workplace.