CLASSIFICATION OF FIRES

CLASSIFICATION OF FIRES

Fires are classed according to fuel and most effective extinguishing agent.

Class A

Fire involving common combustion material and which can be extinguished by use of water or water solution in form of jet and spray e.g. materials include wood, wood based material, cloth, rubber, and certain plastics.

Class B

Fires involving flammable or combustion liquids, paints, varnishes, greases and similar products, either miscible or immiscible with water.

Extinguishing agents include water spray, foam, carbon dioxide and dry chemicals.

Class C

Fires that involve gases or liquid gases in the form of a liquid spillage or a liquid or gas leak. Gases include methane, butane etc.

Foam or dry chemicals may be used to control class c fires involving shallow liquid spills, water in the form of spray is used to cool the containers.

Class D: 

Fires that involve combustion metals, e.g. sodium, magnesium etc.

Extinguishing agents like water, CO2 and bicarbonates are infective and hazardous if used.

Powered graphite, powered talc, soda ash, limestone and dry sand are normally suitable for extinguishing class d type fires.

Class K:

Class K fires involve combustible cooking media such as oils and grease commonly found in commercial kitchens. The new cooking media formulations used form commercial food preparation require a special wet chemical extinguishing agent that is specially suited for extinguishing and suppressing these extremely hot fires that have the ability to reflash.

Electrical Fires

Electrical fire by itself does not constitute a class since any fire involving or started by electrical equipment will be a fire of class a, b, c or d.

In case of a fire involving electrical equipment, electricity supply to the respective equipment must be cut off and an extinguishing medium appropriate to what is burning must be used.

NOTE: Although ABC and BC Dry Chemical extinguishers can control a fire involving electronic equipment, the National Fire Code (NFPA 75-1999 edition), Section 6-3-2, specifically advises against dry-chemical extinguishers for fires involving computers or other delicate electronic equipment due to the potential damage from residues.

Standard for the Protection of Electronic Computer/Data Processing Equipment

6-3.2 Listed extinguishers with a minimum rating of 2-A shall be provided for use on fires in ordinary combustible materials, such as paper and plastics. Dry chemical extinguishers shall not be permitted."

Class F:

New class specifically dealing with high temperature (  360°C) cooking oils used in large industrial catering kitchens, restaurants and takeaway establishments’ etc. Cooking oil fires, because of their high auto-ignition temperatures, are difficult to extinguish.

Conventional extinguishers are not effective for cooking oil fires, as they do not cool sufficiently or may even cause flash back, thereby putting the operator at risk.  These extinguishers contain a specially formulated wet chemical which, when applied to the burning liquid, cools and emulsifies the oil, extinguishing  the  flame,  sealing  the  surface  and preventing re-ignition.