. Classification of
fires
Internationally accepted classification of fires is as follows.
Class 'A'
These are fires involving solid materials normally of an organic nature (compounds of carbon), in which combustion generally occurs with
the formation of glowing embers.
Class A fires are the
most common.
Effective extinguishing agent is generally
water in
the form of
a jet or spray.
Class
'B'
These are fires involving liquids
or liquefiable solids.
For the purpose of choosing effective
extinguishing agents, flammable liquids
may be divided into two groups:
i) Those that are miscible with water, and
ii) Those that are immiscible
with water.
Depending on (i) and (ii), the extinguishing agents include water spray, foam, vapourising liquids, carbon dioxide
and chemical powders.
Class 'C'
These are fires involving gases or liquified
gases in the form of a
liquid spillage,
or a liquid or gas leak, and these include
methane, propane, butane,
etc. Foam or dry chemical
powder can be used to control fires
involving shallow liquid
spills. (water in the form of spray is
generally used to cool the containers.)
Class 'D'
These are fires involving metals.
Extinguishing agents containing water are ineffective,
and even dangerous. Carbon dioxide and the
bicarbonate classes of dry chemical powders may also be hazardous if applied to most metal fires. Powdered graphite, powdered talc, soda ash, limestone and dry sand are normally suitable for class D
fires. Special
fusing powders have been
developed for fires involving some metals, especially the radioactive
ones. Presently special dry chemical
powders have been developed
for extinguishing metal fires.
