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.
