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Combustion Process

Wildland fire behavior is dependent upon understanding the combustion process, the factors that contribute to fire behavior, and how the environment plays a role in the fire process. All of these factors play a role in effective fire control, extinguishment, firefighter safety, and forest management.

Combustion Process: fire is a by product of combustion. fire Three elements must be present for for the fire to occur: heat, oxygen, fuel, and the chemical chain reaction. It is often referred to as the "fire tetrahedron'.

Fire Tetrahedron

Oxygen is in abundant supply for wildland fires. The fuels can exist in three types of matter: solid, liquid, and gas. Only gases burn. The solids or liquids must convert into a gas form with the use of heat through the process of pryrolysis.

The heat evaporates the moisture in the fuel and causes the ignition of the fuel. This is dependent on the type of fuel and the percentage of atmospheric moisture.

Heat Transfer can be takes place by three methods: conduction, convection, and radiation.

Conduction is not usually a concern with wildland fires. Conduction is the transfer of heat between two or more objects. The object with the heat transfers from the warmer one to the cooler object until the temperature is the same. Materials found in wildland fires are often poor conductors of heat.

Convection is the transfer of heat through the movement of liquid or gas. Wildland fires the gases often rise on a column. Sparks, embers, and burning twigs are often carried in this column. These materials are often ignited and can be carried downwind of the fire, resulting in spot fires.

Radiation radiation is heat energy that can by transferred by short energy waves through air. These waves are often called infrared red rays. This heat preheats and dehydrates exposed fuels and establishes pyrolysis. Radiated heat is a major concern for wildland fires and the safety of firefighters.

Controlling the combustion process can be accomplished by four different means: