Nitrogen PSA Generators: With rising energy costs, the ROI is better than ever! On Site’s proven Nitrogen PSA Generator technology gives you quick returns on your investment and stable year-to-year gas costs. How it works: These are PSA (Pressure Swing Adsorption — you read correctly — it’s ad-, not ab-) nitrogen generating systems. Purity from 95-99.9995%, flow lab to 35,000 SCFH. Each unit has two adsorber beds filled with a carbon molecular sieve (CMS). Compressed air enters one end of a bed. While the smaller oxygen molecules are adsorbed by the CMS, the larger nitrogen molecules pass through the sieve and are stored. Once the tube is saturated with oxygen, the first adsorber releases the gas, and the second adsorber starts the process over again.