Classification of Fire
To make it easier to select the appropriate extinguishing media according to the nature of the material undergoing combustion, fires are arranged in 'Classes'. The four classes of fire are given below.
Fires in ordinary combustible materials such as wood, cloth, paper, rubber and many plastics are classified under this. In general fires involving solid materials, usually of an organic nature, in which combustion normally takes place with the formation of glowing embers.
Water is the best extinguishing medium for Class A fires. Some Dry Chemical Powder(DCP) are also used.
Include fires involving liquids or liquefiable solids. Fires in flammable liquids, oils, greases, tars, oil based paints, lacquers, etc.
Foam is the best extinguishing medium for Class B fires. But its reactivity should be ensured in case of Chemical fires.
Fires involving gases. Flammable gases such as methane, natural gas, acetylene, etc.
Dry Chemical Powder is widely used for extinguishing gaseous fires. Its ability to cut the chain reaction in the combustion process makes it suiable for the purpose.
Fires involving metals, including magnesium, zirconium, sodium, lithium, potassium, etc.
Steam, Dry Chemical Powder can be used against meal fires.
What about Class E ?
According to 'International Organisation for Standardisation' (ISO) and 'National Fire Protection Association' (NFPA) 'Class E' does not exist. Before it was classified as 'electrical fires'. But the fact is that material burning due to electrical fire may be classified under other classes A, B, C, or D. Hence 'Class E' no longer exists.