Methods of extinction

Because three ingredients are necessary for fire to occur,it follows logically that if one or more of these ingredients is removed,fire will be extinguished. Basically three methods are employed to extinguish a fire:removal of heat (cooling); removal of fuel (starving); and removal or limitation of oxygen (blanketing or smothering).
Removal of heat
If the rate of heat generation is less than the rate of dissipation,combustion cannot continue. For example,if cooling water can absorb heat to a point where more heat is being absorbed than generated,the fire will go out.
Removal of fuel
This is not a method that can be applied to fire extinguishers. The subdividing of risks can starve a fire,prevent large losses and enable portable extinguishers to retain control; for example,part of a building may be demolished to provide a fire stop.

The following advice can contribute to a company’s fire protection programme:
1.What can cause fire in this location,and how can it be prevented?
2.If fire starts,regardless of cause,can it spread?
3.If so,where to?
4.Can anything be divided or moved to prevent such spread?

Removal or limitation of oxygen
It is not necessary to prevent the contact of oxygen with the heated fuel to achieve extinguishment. It will be found that where most flammable liquids areconcerned,reducing the oxygen in the air from 21 to15 per cent or less will extinguish the fire. Combustion becomes impossible even though a considerable proportion of oxygen remains in the atmosphere. This rule applies to most solid fuels although the degree to which oxygen content must be reducedmay vary. Where solid materials are involved theymay continue to burn or smoulder until the oxygenin the air is reduced to 6 per cent. There are alsosubstances which carry within their own structuressufficient oxygen to sustain combustion.