Document RpQDRanOXGm3J6anQ9De1XnKB

FIRE PROTECTION Fig 33-10 The "Fire Pyramid" of today illustrates a fourth important way that a fire can be extinguished inhibit the flame chain reaction Simple isometric view is at right. Relative position on diagrams is unimportant as all factors ore interdependent. the blanket is maintained long enough For the combustible material to cool below its self-igmbon temperature and if no ignition .sources are present Carbon dioxide and vaporizing bquid are of limited value on fires involving wood, paper, or materials that furnish much of their own oxygen supply when burning, be cause the blanket usually cannot be mamtamed long enough for all smoldering igni tion sources to be extinguished In the field of fire prevention, the princi pal of separating oxygen from the fuel sup ply is applied when an inert gas is used to purge operations involving flammable va pors, dusts, and other combustible materials under confined conditions when a source of ignition may exist Interrupting the reaction Recent studies in fire chemistry have re sulted in certain revisions and expansions m the theories of fire extinguishment In analyzing the anatomy of a fire, the ongmal fuel molecules appear to combine with oxy gen in a senes of successive intermediate stages, called branched-chain reactions, in arriving at the final end products of com bustion It is these intermediate stages which are responsible for the evolution of flames As molecules fragmentize in these 33-15