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