As the temperature is raised to a level at which {TAIL ~ the heating elements} would be damaged, {HEAD ~ a substantially neutral atomsphere} is maintained in the chamber 
As the temperature is raised to a level at which { TAIL ~ the heating elements } would be damaged , { HEAD ~ a substantially neutral atomsphere } is maintained in the chamber
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH