The principle of pressure swing Adsorption(PSA) Oxygen Generator is the diffusion and adsorption of the nitrogen in the compressed air into zeolite molecular sieve(ZMS)

The oil-free and dust-free compressed air enters one of the two adsorption towers (filled with ZMS), The nitrogen is then removed as the compressed continues upward through the ZMS. Oxygen diffuses through the ZMS pore structure and nitrogen is preferentially retained on the ZMS surface at a higher rate than the oxygen .Air separation occurs in one tower for a period of time before the tower switching occurs at the end of period, pressure is equalized between the two towers.

The compressed air is switched to the second tower where the process begins again. The adsorption tower going off-line is depressurised down to atmospheric pressure. This depressurisation regenerates the ZMS by removing nitrogen from ZMS, thus preparing the sieve for reuse in the next cycle.