pressure swing adsorption principle CSS3 animation of the principle of pressure swing adsorption to purify oxygen from air by CMG Lee. (I) denotes the air input, (O) the oxygen output, (E) the exhaust, (A) adsorption and (D) desorption. (1) and (2) show alternating adsorption and desorption. 1. O I E D A 2. O I E A D