Inert gas
Inert gas is produced on board commercial and military aircraft in order to passivate fuel tanks. On hot days, fuel vapor in fuel tanks may otherwise form a flammable or explosive mixture which if oxidized, could have catastrophic consequences. Conventionally, Air Separation Modules (ASMs) have been used to generate inert gas. ASMs contain selectively permeable membranes. They are fed compressed air which drives the separation of oxygen from the air. For fuel tank passivation, it is not necessary to remove all oxygen, but rather enough to stay below the lean flammability limit and the lean explosion limit.