{HEAD ~ A minor amount} of fluorocarbon vapor is also displaced as {TAIL ~ all air} is purged from the chamber 
is displaced as
{ HEAD ~ A minor amount } of fluorocarbon vapor is also displaced as { TAIL ~ all air } is purged from the chamber
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH