A multiple vessel cascade gas enrichment adsorber is provided herein. Two sets of adsorption chambers are provided, each comprising one primary vessel and one secondary vessel, and optionally also a tertiary or further vessel, and each containing a suitable adsorbent, e.g., 5 A molecular sieve adsorbent...http://www.google.com.au/patents/US4321069?utm_source=gb-gplus-sharePatent US4321069 - Multiple vessel cascade gas enrichment system
