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