How Does a Fire Extingusher Work?
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The Basics
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Fire extinguishers work by taking away or altering one of the three elements required for a fire to burn: fuel, oxygen and heat. Fire extinguishers are filled with a particular agent that is released through pressure. Within the fire extinguisher is a container of compressed gas. The safety pin keeps the valve of this chamber from opening. When the pin is released and the lever is activated, the compressed gas forces the extinguishing agent through the nozzle. The agent should be directed at the fuel of the fire rather than the flames.
Types Of Extinguishing Agents
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There are four basic types of extinguishing agents used in fire extinguishers: water, halon, dry chemical and carbon dioxide. Water extinguishers are pressurized with oxygen and are designed to remove the heat from the fire. Halon extinguishers are designed to disrupt the chemical action that allows a fire to burn. Dry chemical extinguishers use, essentially, baking soda to smother the fire and deprive it of oxygen. CO2 extinguishers also smother the fire. CO2 is heavier than oxygen and displaces it from the area. CO2 is also very cold and eliminates the heat from the fire.
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Classes
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Certain agents will not work on certain fires. For instance, using a water extinguisher on a grease fire will spread the fire, not put it out. Extinguishers are, therefore, rated based on the type of fire they should be used on. Class A extinguishers are for common combustibles like paper and wood. Class B extinguishers are for grease and oils, C class is rated for electrical fires and Class D for chemical fires. Extinguishers also have a numerical rating to designate the amount of fire that they can effectively handle.
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