However, such change cannot be fully understood until the process of fire in forests itself is understood. The Fire Triangle Fire is a chemical reaction of any substance that will ignite and burn and leads to a release of energy in the form of heat and light. An external source of heat is generally needed to start a fire. A fire needs at least 16 per cent oxygen in the air supporting it - generally, air contains about 21 per cent oxygen. Heat is energy in disorder, and the degree of that disorder is measured as temperature.
Fuel is considered any material capable of burning.
In forests, this includes living vegetation, branches, needles, standing dead trees, leaves, and human-built wooden structures. The manner in which fuels ignite, flames develop and wildfire spreads is collectively referred to as fire behaviour. It is determined by the quantity and type of fuel, the weather conditions and the region's topography. Fuel composition is further divided by size, chemical make-up, density and arrangement. These determine the amount and type of fuel to burn.