Fire tetrahedron is a four-sided geometric representation of the four factors necessary for fire:
Fuel (any substance that can undergo combustion), Heat (heat energy sufficient to release vapor from the fuel and cause ignition), Oxidizing agent (air containing oxygen), and Uninhibited chemical chain reaction (sufficient exothermic reaction energy to produce ignition).
The fuel/air ratio must within flammable limits, which describes the amount of vapor in air necessary to propagate flame. Removing any of these four factors will prevent, suppress, or control the fire.
Tetrahedron can be described as a pyramid which is a solid having four plane faces. Essentially all four elements must be present for fire to occur, fuel, heat, oxygen, and a chemical chain reaction. Removal of any one of these essential elements will result in the fire being extinguished.