PSA technology can be used for Oxygen production too, by selecting a different molecular sieve. The process is exactly the same already described for nitrogen. VPSA technology is used in massive production of gaseous oxygen. High quality air stream is blowed at low pressure into molecular sieves placed inside two high capacity vessels. Regeneration of sieves is realized by means of vacuum generated by a pump. Alternative cycles of adsorption and regeneration assures continuous massive oxygen production at low pressure with high energy efficiency, caused by use of a blower instead of a compressor. If high pressure oxygen is needed, a booster integrate the process.