The certain pressured air is used as raw materials to achieve the separation of oxygen gas and nitrogen gas by using the difference of permeation rate between oxygen and nitrogen through the hollow fiber membranes . Compared with PSA nitrogen plants , the membrane nitrogen gas generator have the advantages of smaller volume , non - switching valve , no noise , rapid gas production ( ≤3 minutes ) , easy capacity increase , etc., it is particularly suitable for the small nitrogen user needing nitrogen purity ≤ 98% . The price of membrane generator would be higher 80% than PSA generator , when the nitrogen purity is needed above 99% . The device is relatively accepted to the user with less sensitivity to price , less requirement about nitrogen purity ( 95% to 99% ) , but with more concerning of device sizes as small as possible and easy to expand production capacity . The main application of membrane nitrogen gas generator is used in the oil or coal fire extinguishing systems and nitrogen inert gas protection of ship or ocean plaform .