{HEAD ~ A gas escape} and monitor pipe 22 at the lowest level of the gas in the area 23 within the housing 18 allows for {TAIL ~ gas} to escape, and can give an indication of the lowest level of the reducing gas at 23 
allows for
{ HEAD ~ A gas escape } and monitor pipe 22 at the lowest level of the gas in the area 23 within the housing 18 allows for { TAIL ~ gas } to escape , and can give an indication of the lowest level of the reducing gas at 23
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH