Characteristics of flammable gas mixtures
Gas-phase Explosion Hazards - Flammability of Gas and Vapors

Flammable gas phase

A gaseous phase is flammable when it allows a flame to propagate. This may be a combustion flame involving a fuel gas and an oxidizing gas. It can also be a flame resulting from the decomposition of an unstable gas, either pure or mixed with an inert gas.

Flammable mixtures

A gas mixture is flammable when it consists of a fuel gas, or a mixture of fuel gases, and an oxidizing gas, or a mixture of oxidizing gases.

– The fuel can be a hydrocarbon such as natural gas or propane, hydrocarbon vapors, solvents, hydrogen, or even the vapor of an oxidizable metal.

– The oxidizer can be oxygen, air, mixtures of oxygen and nitrogen of varying composition, but also oxidizing gases such as ozone, chlorine,...