After removing solid impurities such as oil, dust and most of gaseous water, compressed air enters the adsorption tower equipped with zeolite molecular sieve. Nitrogen, carbon dioxide and water vapor in the air are absorbed by adsorbent, while oxygen is separated through the adsorption bed. When the adsorbed impurities in the adsorption tower reach a certain degree, they will enter the atmosphere for desorption and regeneration of the adsorbent. The adsorption and separation system composed of two and three towers circulates and switches under the automatic control of PLC or DCS system to complete the continuous oxygen production. This process is called PSA (pressure swing absorption) oxygen production principle.