PSA stands for pressure swing adsorption. Absorption is actually a process which involves a chemical change. Generally accepted use of the term "absorb" implies a sponging effect. The term has been misused for a long time. Since nothing we do is chemical, only physically separating molecules, the process is correctly called adsorption. It’s the process of separating molecules of gas from each other.
We use compressed air to pressurize a vessel filled with a material, either carbon or zeolites, which actually sift molecules by physical or structure. By forcing air into this pressure vessel or sieve bed filled with sieve, we cause N2 or O2 molecules to be trapped in the sieve, while the other gas floats free in the bed. After a period of time, we release a bit of the pressure in the sieve bed to draw off the O2 or N2 molecules and collect them in a surge/storage tank for use by the application. We then open a valve in the sieve bed and release all of the pressure in the sieve bed, forcing out the captured molecules of the unwanted gases and cleansing the sieve for the next cycle.
The molecules of gas released into the air immediately combine back to air’s ambient percentages since we are, in effect, diluting all of the air on the planet with our released gas. With our systems, we use two sieve beds that work at opposing ends of the cycle to provide a more consistent flow of our captured gas into the surge tank.