The fire triangle is composed of oxygen, heat and fuel. It is sometimes called the fire tetrahedron because of a fourth component, chemical reactions. Fires start with just the first three elements, but they cannot remain burning without the heat produced through chemical reactions.
Fires are put out by removing one or more elements in the fire triangle or by breaking the chemical reaction that creates the flammable gases that maintain heat. Fires that are not put out during the ignition stage spread by the transference of heat energy from the flames. Disastrous conditions such as rollovers and flashovers can occur if fires are left burning in unventilated spaces.