General principles and vocabulary
Standardized fire behaviour tests

For combustion to occur, four basic elements must be present:

• a gaseous fuel ;

• an oxidizer, usually oxygen from the air;

• energy, produced in most cases by a thermal source;

• adapted chemical kinetics.

This is illustrated by the figure 1 , generally referred to as the fire tetrahedron. As only gaseous fuels are involved in combustion, solids must first be heated to produce combustible vapors, possibly passing through an intermediate liquid stage.