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Basic Elements of a Fire |
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FIRE
Fire burns because three elements are present - heat,
fuel and oxygen. In technical language, fire is a
chemical reaction: It happens when a material unites
with oxygen so rapidly that it produces flame. Think of
fire as a triangle. If any one of three sides - heat,
fuel or oxygen - is taken away, the fire goes out. This
is the basis for fire extinguishment. Heat can be taken
away by cooling, oxygen can be taken away by excluding
air, fuel can be removed to a place where there is no
flame, chemical reaction can be stopped by inhibiting
the oxidation of the fuel. |
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REMOVE HEAT
Cooling a fire calls for the application of something
which absorbs heat. Although there are others, water is
the most common cooling agent. Water is commonly applied
in the form of a solid stream, finely divided spray or
incorporated in foam. |
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REMOVE FUEL
Often, taking the fuel away from a fire is difficult and
dangerous, but there are exceptions. Flammable liquid
storage tanks pan be arranged so their contents can be
pumped to an isolated empty tank in case of fire. When
flammable gases catch fire as they are flowing from a
pipe, the fire will go out if the flow can be valved
off. |
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REMOVE OXYGEN
Oxygen can be taken away from a fire by covering it with
a wet blanket, throwing dirt on it or covering it with
chemical or mechanical foam. Other gases which are
heavier than air, such as carbon dioxide and vaporizing
liquid, can be used to blanket the fire, preventing the
oxygen from getting to the fire. |
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STOP THE REACTION
Studies made during recent years have indicated that the
familiar statement, "Remove heat, remove fuel, or remove
oxygen, to extinguish a fire" does not apply when dry
chemical or halogenated hydrocarbons are used as the
extinguishing agents. These agents inactivate
intermediate products of the flame reaction resulting in
a reduction of the combustion rate (the rate of heat
evolution) and extinguishes the fire. A more detailed
discussion of this action appeared in the April 1960
issue of the quarterly of the NFPA under the title of
"The Chemical Aspects of Fire Extinguishment." |
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