Fire triangle
[1] The triangle illustrates the three elements a fire needs to ignite: heat, fuel, and an oxidizing agent (usually oxygen).
In large fires where firefighters are called in, decreasing the amount of oxygen is not usually an option because there is no effective way to make that happen in an extended area.
[6] Therefore, inert agents (e.g. dry sand) must be used to break the chain reaction of metallic combustion.
A fire based on a reaction with these oxidizers can be very difficult to put out until the oxidizer is exhausted; that leg of the fire triangle cannot be broken by normal means (i.e., depriving it of air will not smother it).
There are also many other ways to bring sufficient activation energy including electricity, radiation, and pressure, all of which will lead to a temperature rise.
The temperature at which a liquid produces sufficient vapor to get a flammable mix with self-sustainable combustion is called its flash-point.
Introducing sufficient quantities and types of powder or gas in the flame reduces the amount of heat available for the fire reaction in the same manner.
Fuel separation is an important factor in wildland fire suppression, and is the basis for most major tactics, such as controlled burns.
In the gas phase, i.e. in the flames or in the smoke, the combustible can not be separated from the oxidizer, and the only possible action consists of cooling down.
Lastly, fuels is the term to describe what burns in a single flame to the range of materials burnt in a spreading wildfire, but fuels vary over larger space and time scales in what is called vegetation.
The largest scale, in contrast, describes the fire regime concept.
Global climate change drives many of the factors involved in the 'wildfire' and the 'fire regime' triangles.
