Exercise 4. Read text C Fire Extinguishing Theory

The extinguishment of fires is based on an interruption of one or more fire ingredients. With flaming combustion the fire may be extinguished by reducing temperature, eliminating fuel or oxygen, or by stopping the uninhibited chemical chain reaction. If a fire is in the smoldering phase, only three extinguishment options exist: reduction of temperature, elimination of fuel, or oxygen.

One of the most common methods of extinguishment by cooling is dependent on cooling the fuel to a point where it doesn’t produce sufficient vapor to burn. Solid fuels and liquid fuels with high flash points can be extinguished by cooling. Low flash point liquids and flammable gases cannot be extinguished by cooling with water as vapor production cannot be sufficiently reduced.

Reduction of temperature is dependent on the application of an adequate flow in proper form to establish a negative heat balance.

In some cases, a fire is effectively extinguished by removing the fuel source. This may be done by stopping the flow of liquid or gaseous fuel or by removing solid fuel in the path of the fire. Another method of fuel removal is to allow the fire to burn until all fuel is consumed.

The method of extinguishment by oxygen dilution is the reduction of the oxygen concentration in the fire area. This can be accomplished by introducing an inert gas into the fire or by separating the oxygen from the fuel. This method of extinguishment will not work on self-oxidizing materials or on certain metals as they are oxidized by carbon dioxide or nitrogen, the two most common extinguishing agents.