The nature of fire: why it is dangerous and how it develops

Combustion is possible only when three conditions coincide — the "fire triangle": fuel (wood, fabric, paper, fuel), an oxidizer (oxygen in the air) and a source of high temperature (a spark, open flame, hot object). Remove any side and combustion stops. All extinguishing methods rely on this: cooling, cutting off the fuel and displacing oxygen. A fourth element is often added — the chain chemical reaction (hence the "fire tetrahedron").

The main danger of a fire is not the flame itself but the speed at which it develops and the products of combustion. A fire passes through stages: the initial one (much smoke, rising temperature), developed burning and the most dangerous moment — flashover, when at a ceiling temperature of about 500–600 °C almost all combustible surfaces ignite at once. From the first open flame to flashover only a few minutes may pass.

The main killer in a fire is not fire but smoke and toxic gases: carbon monoxide (CO), hydrogen cyanide, hydrogen chloride. Carbon monoxide is odorless but binds to blood hemoglobin hundreds of times more readily than oxygen, causing rapid poisoning and death. Most fire victims die from inhaling the products of combustion and from suffocation. So the main task is to reach smoke-free air as fast as possible, not to "wait out" the fire in place.