The oxygen concentrator is a device used to provide oxygen therapy to a patient at concentrations substantially higher than those available for the ambient air quality. They are used as a source more secure, less expensive, and cheaper alternative to tanks of compressed oxygen. Oxygen concentrators are also used to provide a cheap source of oxygen in industrial processes. The oxygen concentrator is capable of continuous delivery of oxygen and has an internal mechanism based on two cylinders, filled with a zeolite material, which selectively absorbs the nitrogen in the air. In each cycle, the air flows through a cylinder at a pressure of about 20 lbf / in ² (138 kPa, or 1.36 atmospheres), and in that nitrogen molecules are captured by the zeolite, while the other cylinder, is riespulsa out at atmospheric pressure environment that allows the release of nitrogen to dissipate. Standard units have cycles of about 20 seconds, and allow a constant supply of oxygen at a flow rate of up to about five liters per minute (LPM) at concentrations from 50 to 95%. This process is called pressure swing absorption (PSA).