A stationary assembly of mains electricity (AC-powered) devices designed to concentrate oxygen (O2) from ambient air and then deliver the concentrated O2, with purity of up to 99.5%, to the hospital medical gas supply system. It may produce high-purity O2 using pressure swinging adsorption (PSA) technology which processes air through internal molecular sieves having a large total surface area to separate nitrogen (N2) from the air. It typically consists of an air compressor, refrigeration dryer, water and oil separators, high pressure O2 pump and various storage tanks. The concentrated O2 is delivered via the medical gas supply system to the user and/or a gas cylinder filling station.