Carbon molecular sieve is a carbon-based adsorbent with some characteristics of activated carbon and molecular sieve. Carbon molecular sieve has a very small micropore composition, with a pore size distribution between 0.3nm and 1nm. Gas with a smaller diameter (oxygen) diffuses faster and enters the solid phase of the molecular sieve more, so that the gas phase can be enriched in nitrogen. After a period of time, the adsorption of oxygen by molecular sieve reaches equilibrium. According to the different characteristics of carbon molecular sieve for adsorbing gas under different pressures, the pressure is reduced to release carbon molecular sieve from adsorbing oxygen. This process is called regeneration. The pressure swing adsorption method usually uses two towers in parallel, alternately performing pressure adsorption and decompression regeneration, so as to obtain a continuous nitrogen flow.