{HEAD ~ The chamber} is sealed upon purging of all the air and is maintained in a pressurized state for {TAIL ~ a period} of time 
is maintained for
{ HEAD ~ The chamber } is sealed upon purging of all the air and is maintained in a pressurized state for { TAIL ~ a period } of time
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH REL REL OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH