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Selecting a Fire Extinguisher - Understanding the what the ratings mean, choosing the right type of Fire Extinguishers

Choosing the right fire extinguisher - All About Fire Extinguishers Ratings

The classification letters on fire exxtinguishers can be confusing, but it is important to use the right type of fire extinguisher for the type of fire you are trying to put out. The chart below should make it easy to select the best type of fire extinguisher for your home or office.

Classification of Fire Extinguishers

There are five general classifications of fires and extinguishing agents. They are each designed to put out different kinds of fires.

class A fire extinguisher class B fire extinguisherclass C fire extinguisherclass D fire extinguisher class K fire extinguisher

For use with ordinary materials like cloth, wood and paper. Class A fires are those that involve ordinary combustible materials such as wood, paper, cloth, rubber and plastics. The quenching and cooling effects of water or of solutions containing large amounts of water are the most effective means of extinguishing this type of fire

Often used in homes and businesses

For use with combustible and flammable liquids like grease, gasoline, oil and oil-based paints. Class B fires are those that occur in the vapor-air mixture over the surface of flammable liquids such as gasoline, oil, grease, paints and thinners. The limiting of air (oxygen) or the combustion inhibiting effect is the most effective measure against incipient fires of this class. Water must not be used on Class B fires because it tends to spread the fire.

Often used in homes and businesses

For use with electrical equipment like appliances, tools, or other equipment that is plugged in. Class C fires are those that occur in or near energized electrical equipment where non-conducting extinguishing agents must be used. Water must never be used on Class C fires.

Often used in homes and businesses

For use with flammable metals Class D fires are those that involve combustible metals such as magnesium, titanium, zirconium and sodium. Water must never be used on class D fires. A Class D powdered extinguishing agent should be used.

Often used in factories

For use with vegetable oils, animal oils and fats in cooking appliances.

Often used in commercial kitchens (restaurants, cafeterias, catering businesses)

Multipurpose fite extinuishers

class A fire extinguisherclass B fire extinguisherclass C fire extinguisher

There are also multipurpose fire extinguishers that might be labeled "B-C" or "A-B-C." Most Big Box stores and home improvement stores, like Home Depot and Lowes, carry multipurpose fire extinguishers that cover Class A through Class C. The A-B-C type fire extinguishers are usually the best choose for use in homes.

Appendix 1-Fire Extinguisher Size and Placement for Class A Hazards

Light(Low)Hazard Occupancy Ordinary(Moderate)Hazard Occupancy Extra(High)Hazard Occupancy
Minimum rated single extinguisher 2-A 2-A 4-A*
Maximum floor area per unit of A 3,000 sq ft** 1,500 sq ft. 1,000 sq ft.
Maximum floor area for extinguisher 11,250 sq ft** 11,250 sq ft** 11,250 sq ft**
Maximum travel distance to extinguisher 75 ft. 75 ft. 75 ft.

* Two 2 1/2 gallon (9.46 L) water type extinguishers can be used to fulfill the requirements of one 4-A rated extinguisher.

** See pamphlet 10, Portable Fire Extinguishers, National Fire Protection Association, 1981 Edition.

Appendix 2-Fire Extinguisher Size and Placement for Class B Fires

Other than for Fires in Flammable Liquids of Appreciable Depth

Type of Hazard (m 2 ) Basic Minimum Extinguisher Rating Maximum Travel Distance to Extinguishers (ft.)
Light (Low)
  • 9.15
5B 30
  • 15.25
10B 50
Ordinary (Moderate)
  • 9.15
10B 30
  • 15.25
20B 50
Extra (High)
  • 9.15
40B 30
  • 15.25
80B 50

Appendix 3-Fire Extinguisher Size and Placement for Class C Hazards

Extinguishers with Class C rating shall be required where energized electrical equipment may be encountered which would require a non-conducting extinguishing medium. This will include fire either directly involving or surrounding electrical equipment. Since the fire itself is a Class A or Class B hazard, the extinguishers are sized and located on the basis of the anticipated Class A or B hazard.