{HEAD ~ Preferably oxygen} is displaced by {TAIL ~ a co current flow} of cold nitrogen, following which krypton and xenon are collected by thermal regeneration and counter current purging with hot nitrogen 20, thus avoiding potentially explosive concentrations of hydrocarbons and oxygen in the desorbed gas 22 
is displaced by
{ HEAD ~ Preferably oxygen } is displaced by { TAIL ~ a co current flow } of cold nitrogen , following which krypton and xenon are collected by thermal regeneration and counter current purging with hot nitrogen 20 , thus avoiding potentially explosive concentrations of hydrocarbons and oxygen in the desorbed gas 22
HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH