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