Oxygen concentrator is a device to selectively separate and concentrate oxygen in the air. Unlike liquid oxygen, oxygen concentrator is capable of continuous supply. Therefore, oxygen concentrator is being used in various areas, such as in medical fields and households as well as for air conditioner, automobiles and industrial facilities, etc. to which continuous oxygen supply must be carried out over a long period of time. Technologies for oxygen concentration include PSA, VSA, TSA and membrane, etc. Among them, the most generalized method of PSA (pressure swing adsorption) process is the technology to extract and concentrate target gas from a mixture of different gases through pressure change. Using physical absorption and separation property, it does not generate pollutants and safely produce oxygen.

PSA technology became commercialized as it began to be used for air drying by Skarstrom in the 1960s. Separation technology using PSA process, together with improvement in the functions of molecular sieve and new product development, has been widely used for separation and refinement of gases and liquids. PSA process of gas separation is based on the fact that absorption quantity of various gases differs per absorbent. In case there is no change in the amount of gas absorption and separation, the amount of absorption is referred to as the amount of absorption equilibrium and gas holds different amount of absorption equilibrium according to temperature and pressure. As shown in the graph below, increase in pressure leads to increase in absorption amount and vise versa. Resultantly, gas separation takes place by removing gas remaining in gaseous state when the amount of absorption reaches the maximum. In general, oxygen is separated by changing pressure and temperature after injecting mixture of gas (oxygen and nitrogen) to absorbent.

To explain oxygen separation process in more detail, in air, degree of selection of nitrogen in relations to zeolite is higher than the degree of selection of oxygen. Therefore, when increasing pressure by injecting air into absorption tower filled with absorbent, nitrogen is absorbed and oxygen passes through the absorption tower. At the outlet, oxygen of lower degree of absorptive selection is obtained. After a certain period of time, nitrogen with high degree of absorptive selection is absorbed and saturated. As pressure decreases, nitrogen is separated and reproduced. As such, the basic PSA process concentrates substances of weaker absorptive selection through the two stages described above, such as repetition of absorption and separation in absorption tower.