Once vaporized, {TAIL ~ the substance} is withdrawn from the chamber by {HEAD ~ the vacuum producing means} 
Once vaporized , { TAIL ~ the substance } is withdrawn from the chamber by { HEAD ~ the vacuum producing means }
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD