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Extinguishing Agents
Water. Water is primarily a cooling agent. It absorbs heat and cools burning materials more effectively than any other of the commonly used extinguishing agents. It is most effective when it absorbs enough heat to raise the temperature to 100°C (212° F). At that temperature water absorbing still more heat turns to steam, and moves the absorbed heat away from the burning material. This quickly reduces the temperature of the burning material below its ignition temperature, and the fire goes out. Water has an important secondary effect: when it turns to steam, it is converted from the liquid state to the gaseous state, and expands about 1700 times in volume. This great cloud of steam surrounds the fire, displacing the air that supplies oxygen for the combustion process. Thus, water provides a smothering action as well as cooling. Seawater is just as effective in fighting fires as fresh water. In fact, hard water, soft water, seawater, and distilled water are equally effective against Class "A" fires. Carbon dioxide. Carbon dioxide, C02, has a number of properties making it useful for extinguishing fires. It is non- combustible and does not react with most substances. Since it is a gas, it can generate and spread to all parts of a fire area. It is a non- conductor of electricity and does not damage electronic equipment. Carbon dioxide is especially effective and safe for all confined fires. It acts as an inert blanket and being heavier than air it excludes oxygen very efficiently from a fire on the floor of a building. It is not effective in an elevated location or outdoors where the wind can blow the gas away. Foam. Protein foam compounds are the most widely used agents, extinguishing flammable liquid fires. Protein foam of good quality is resistant to the effects of heat and fuels and is capable to flow over the fuel surface to form a cohesive blanket. This blanket of foam extinguishes the fire by excluding air and suppressing the release of flammable vapour from the fuel surface. Its water content also provides cooling the fuel and adjacent surface. Fluoroprotein foam has the excellent stability and heat resistance as protein foam but it is more effective in suppressing the release of volatile fuel vapours. In addition to its primary use in extinguishing flammable liquid fires, foam can be used in other ways, such as extinguishing fires in enclosed spaces. Дата добавления: 2015-09-18 | Просмотры: 665 | Нарушение авторских прав |