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Science of extinguishment

There are four elements needed to start and sustain a fire and/or flame: temperature, a fuel, an oxidizing agent (oxygen), and a chemical reaction. A fire can be extinguished by taking away any of the four components.

The fuel is the substance being oxidized or burned in the combustion process. The most common fuels contain carbon along with combinations of hydrogen and oxygen. Heat is the energy component of a fire. When it comes into contact with a fuel, it provides the energy necessary for ignition, causes the continuous production and ignition of fuel vapors or gases so that the combustion reaction can continue, and causes the vaporization of solid and liquid fuels. The resulting self-sustained chemical chain reaction is complex and requires fuel, an oxidizer, and heat energy to come together in a very specific way. An oxidizing agent is a material or substance that will release gases, including oxygen, when the proper conditions exist. It is crucial to the sustainment of a flame or fire.

Using water is one common method to extinguish a fire. Water extinguishes a fire by cooling, which removes heat because of water’s ability to absorb massive amounts of heat as it converts to water vapor. Without heat, the fuel cannot keep the oxidizer from reducing the fuel in order to sustain the fire. Water also extinguishes a fire by smothering it. When water is heated to its boiling point, it converts to water vapor. When this conversion takes place, it dilutes the oxygen in the air above the fire, thus removing one of the elements that the fire requires to burn. This can also be done with foam.

Another way to extinguish a fire is fuel removal. This can be accomplished by stopping the flow of liquid or gaseous fuel, by removing solid fuel in the path of a fire, or by allowing the fire to burn until all the fuel is consumed, at which point the fire will self-extinguish.

One final extinguishing method is chemical flame inhibition. This can be accomplished by applying dry chemical or halogenated agents that interrupt the chemical chain reaction and stop flaming. This method is effective on gas and liquid fuel because they must have flame to burn.

Sound waves have been successfully used in a device fabricated by two George Mason University senior engineering students, Viet Tran and Seth Robertson, but the procedure is still awaiting a patent (2015).