Pressure Swing Adsorption (PSA) technique is utilised to obtain Oxygen from atmospheric air. Compressed air at about 4-6 bar, depending on the size of the unit is processed via a compressor or from a compressed air network alternatively in two towers equipped with special grade of Molecular Sieves (Adsorbers A and B). Through the pressure change controlled electronically by valve block D, Nitrogen, moisture and Carbondioxide are adsorbed and desorbed.