fire tetrahedron: a standalone construct

In fire protection, the fire tetrahedron is the teaching model of the four conditions a fire needs simultaneously: fuel, an oxidizer, enough heat, and an uninhibited chemical chain reaction among the burning radicals. It extends the older fire triangle of fuel, heat, and oxygen by adding the chain reaction as a fourth face, which explains how chemical-inhibiting agents such as halons and dry chemicals put out fire without removing heat, fuel, or air. Friedman's Principles of Fire Protection Chemistry and Physics uses it to organise both combustion and extinguishment. The referent is the set of necessary ingredients for sustained flaming combustion, and every suppression method works by removing or interrupting one of its four faces.[1]

Unit

Whether all four combustion requirements are simultaneously present

Recovery means

Not applicable

Measured by

Applied qualitatively: a fire is sustained only while fuel, oxidizer, heat, and the radical chain reaction coexist, and is extinguished by removing any one