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