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 sources of the rare gases neon, krypton, and xenon is the distillation of air using at least two distillation columns.