The physical separation of gases from a mixture at room temperature is the underlying principle of oxygen concentrators. This low energy method has been developed in recent years to allow separation of oxygen from air, and has been applied to all scales of size from an incubator to a complete steelworks. The largest application of oxygen concentrators in medicine has been in the provision of portable, domiciliary machines for the provision of long term home oxygen therapy to patients with chronic lung disease. The prime reason for this development was the dramatic cost savings which could be achieved. The purchase price of a concentrator is about half the cost of a year's supply of oxygen from cylinders.
Nitrogen binds to the zeolite, while oxygen passes through.
As the second column approaches saturation the process is reversed. The life of the zeolite crystals can be expected to be at least 20,000 hours which in most situations would give about 10 years' use. Higher flows result in a loss of concentration, and most machines are flow-limited to prevent this from occurring. In recommending technology from the western world to the developing world it is important to have an established reliability record, and oxygen concentrators certainly meet this requirement. Domiciliary concentrators have been in regular use for more than ten years and have in general proved very reliable.