TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Method: In the method (M1) the oxygen removal from the air stream comprises providing an absorbent material and adsorbing the oxygen onto the adsorbent material by passing the air stream through the adsorbent material. The method (M1) further comprises re-generating the adsorbent material by providing a hydrogen stream and passing the hydrogen stream through the adsorbent material. The passing the nitrogen stream through the fuel cell stack anode comprises passing the nitrogen stream through the fuel cell stack anode after shutdown of the fuel cell stack. The method (M1) further comprises flowing a stream exiting the adsorbent material through the fuel cell stack; heating the adsorbent material during the passing the hydrogen stream through the adsorbent material. The passing the air stream through the adsorbent material comprises passing the air stream through the adsorbent material during start-up of the fuel cell stack. The re-generating the adsorbent material comprises re-generating the adsorbent material after startup of the fuel cell stack. The method (M1) further comprises heating the adsorbent material during the passing the hydrogen stream through the adsorbent material. In the method (M2) the production of a nitrogen-rich stream comprises flowing an air stream through an oxygen adsorbent material to remove at least a portion of the oxygen from the air and to increase the concentration of nitrogen. The nitrogen-rich stream is free of oxygen (less than or equal to 2 wt.%). The method (M3) comprises: providing a first adsorbent material and a second adsorbent material; providing a first nitrogen stream by passing the air stream through the first adsorbent material and passing the first nitrogen stream through the fuel cell stack during shutdown of the fuel cell stack; providing a second nitrogen stream by passing the air stream through the second adsorbent material and passing the second nitrogen stream through the fuel cell stack during start-up of the fuel cell stack; and re-generating the first adsorbent material and the second adsorbent material by providing a hydrogen stream and passing the hydrogen stream through the first adsorbent material and the second adsorbent material, respectively. The hydrogen stream is vented from the first adsorbent material and second adsorbent material through the fuel cell stack. The adsorbent material (first and second) comprises at least one of a carbon structure, a carbon molecular sieve, a zeolite, cerium oxide (CeO), oxygen adsorbing material or reversibly oxidizable oxide materials (preferably CeO and a catalyst). The method (M3) further comprises heating the first adsorbent material and the second adsorbent material during the passing the hydrogen stream through the first adsorbent material and the second adsorbent material. Preferred system: The hydrogen flow line is provided in fluid communication with the adsorber for selectively delivering the hydrogen stream into the adsorber to regenerate the adsorbent material. The purge system further comprises an adsorbent heater provided in thermal contact with the adsorber for heating the adsorbent material; a cathode exhaust distribution line provided in fluid communication with the adsorber for selectively re-generating the adsorbent material by delivering cathode exhaust from the fuel cell stack to the adsorber; a second adsorber comprising a second adsorbent material provided in fluid communication with the air flow line for selectively receiving and removing oxygen from the air stream and delivering a nitrogen stream into the fuel cell stack anode. The system is provided with a hydrogen shunt line in fluid communication with the hydrogen flow line and the adsorber for selectively delivering the hydrogen stream from the hydrogen flow line to the adsorber and re-generating the adsorbent material. EXAMPLE - No suitable example is given.