Inerting

Inerting is a fire and explosion prevention engineering technique that involves the introduction of an inert (non-combustible) gas into a closed system such as a container or process vessel to make a flammable atmosphere oxygen-deficient and non-ignitable. This process relies on the fundamental principle that a combustible or flammable gas can undergo combustion or explode only when mixed with air in the right proportions, and by introducing inert gas, the oxygen concentration is diluted below the limiting oxygen concentration (LOC).

The primary goal of inerting is to prevent the formation of explosive mixtures by using inert gas to reduce the oxygen volume fraction below the maximum permissible oxygen concentration (MPC), making the mixture unable to inflame in the protected space. Unlike purging, which ensures that an ignitable mixture never forms, inerting makes an already ignitable mixture safe through the introduction of inert gas.

Inerting operates on the principle that combustion requires three elements to occur: fuel, oxygen, and an ignition source. By removing or reducing the oxygen component below the critical threshold, the combustion reaction cannot be sustained even if fuel and ignition source are present. During inerting, the oxygen is displaced by a non-reactive gas until a non-ignitable mixture is created.

The process can be applied to different types of systems. For closed systems such as reactors or tanks, inerting can be ensured by maintaining a slight overpressure of inert gas. For open systems, a continuous flow of inert gas is required, and measurements of oxygen concentration may be necessary to ensure adequate protection.

Emergency inerting involves introducing inert gas into the object to be protected, such as a silo, in the event of elevated temperatures or carbon monoxide concentration, serving as an explosion suppressant when a safety failure creates an imminent risk of explosion.