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