Fire control
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- For an article about controllers for the firing of weapons, see Fire-control system
Fire control consists of depriving a fire of fuel, oxygen or heat (see fire triangle) to prevent it from spreading or to put it out entirely. The standard and most common way to control a class-A fire (the combustion of a flammable material with oxygen and heat) is to remove heat by spraying the burning solid fuels with water from a fire-hose connected to a pump. Other methods of controlling a class-A fire would be to "smother" the fire with carbon dioxide, such as from a fire extinguisher, cutting off it's oxygen. In a forest fire, fire control would usually consist of removing fuel in the fire's path and digging trenches - this prevents the fire from gaining new fuel and spreading.
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[edit] Class-B fires
Class-B fires (hydrocarbons and fuels on fire) require much different handling than the standard water approach. Many fuels, such as gasoline or oil float on water, and water would actually end up spreading the fire further. Other fuels, such as coal, will not be put out by water, as fire spreads to the inside of the coal and cannot be reached by water - as soon as the water stops, the fire inside of the coal spreads back out to the outside. Fire control of these fires requires specialized methods, and can be problematic to ordinary fire stations due to the fact that these materials may not always be available.
One way to control a class-B fire would be to dump chemical dust on it - this is also a method for handling class-A fires, and actually tends to be preferable due to the fact that sprayed water tends to cause property damage. Gasoline fires are more often smothered in a cooling protein foam.
[edit] Class-C fires
Class-C fires are electrical fires - fires that are caused by an electrical source and get their heat from electricity. These fires are dangerous because if water is used on them, electrical current will be passed through the stream and back into the firefighter. There are only two ways to deal with this type of fire - take away the oxygen (smother it with foam or a fire extinguisher) or simply turn off the electricity, which will cause the fire to either die out or become a regular class-A fire.
[edit] Ventilation
Most fires spread as hot gases move through the structure. Some fires can be controlled or limited by venting these gases to the outside either horizontally through windows and doors or vertically through existing openings or by cutting holes in the structure's roof. This can aggravate a fire if it introduces new oxygen, or permits a draft past fuel or structure, making professional training in how to perform ventilation required to do it safely - a backdraft (the rapid combustion of a room, nearly akin to an explosion) may result if done incorrectly, or at the very least cause the fire to spread further.
