<P> An air separation plant separates atmospheric air into its primary components, typically nitrogen and oxygen, and sometimes also argon and other rare inert gases . </P> <P> The most common method for air separation is fractional distillation . Cryogenic air separation units (ASUs) are built to provide nitrogen or oxygen and often co-produce argon . Other methods such as membrane, pressure swing adsorption (PSA) and vacuum pressure swing adsorption (VPSA) are commercially used to separate a single component from ordinary air . High purity oxygen, nitrogen, and argon used for semiconductor device fabrication requires cryogenic distillation . Similarly, the only viable source of the rare gases neon, krypton, and xenon is the distillation of air using at least two distillation columns . </P>

Process by which nitrogen is obtained from air on a large scale