Some oxygen 24 passes through and some oxygen and {HEAD ~ xenon} and krypton are adsorbed and recovered during {TAIL ~ bed regeneration} 
recovered during
Some oxygen 24 passes through and some oxygen and { HEAD ~ xenon } and krypton are adsorbed and recovered during { TAIL ~ bed regeneration }
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL