In fire and explosion prevention engineering, inerting refers to the introduction of an inert (non-combustible) gas into a closed system (e.g. a container or a process vessel) to make a flammable atmosphere oxygen deficient and non-ignitable.[1][2]
Inerting relies on the principle that a combustible (or flammable) gas is able to undergo combustion (explode) only if mixed with air in the right proportions. The flammability limits of the gas define those proportions, i.e. the ignitable range. In combustion engineering terms, the admission of inert gas can be said to dilute the oxygen below the limiting oxygen concentration.
Inerting differs from purging. Purging, by definition, ensures that an ignitable mixture never forms. Inerting makes an ignitable mixture safe by introduction of an inert gas.