{TAIL ~ A pressure} of at least 20 psi may be maintained within {HEAD ~ the chamber} 10 
{ TAIL ~ A pressure } of at least 20 psi may be maintained within { HEAD ~ the chamber } 10
TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH