Membrane method
The Membrane method or mixing by gas separation is a method of gas blending to produce nitrox, a breathing gas mostly used for scuba diving.
Nitrox systems use semi-permeable membranes to separate out a portion of the nitrogen in air. Nitrox mixtures, containing between 24% and 40% oxygen (O2), are then delivered to a high-pressure compressor to fill scuba cylinders or storage tanks, or to a low-pressure compressor for pumping to surface-supply divers. Although this compressor is described as the “nitrox compressor”, it is also used for air.