VPSA ( Vacuum pressure Swing Adsorption ) Oxygen gas Generators are based on well proven technology using Zeolite Molecular Sieves (ZMS) & Vacuum system for regeneration . When ZMS is used in the VPSA process, nitrogen Molecules, having a higher diameter than oxygen Molecule, passes through the pores and are adsorbed. Therefore, the Oxygen is recovered, while Nitrogen is adsorbed. Adsorption of Nitrogen Molecules happens at Low pressure, which make it efficient & suitable for higher flow rates. In VPSA based Oxygen gas plants Regeneration process is dine with vacuum pumps, which ensures complete regeneration of ZMS. Adsorptive air separation is a cyclic process, in which adsorbent material is alternately, Fed with pressurised air to produce the required product and Regenerated by vacuum to remove the waste gases from the adsorbent.