A gas escape and monitor pipe 22 at 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 {HEAD ~ the lowest level} of {TAIL ~ the reducing gas} at 23 
of
A gas escape and monitor pipe 22 at 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 { HEAD ~ the lowest level } of { TAIL ~ the reducing gas } at 23
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 OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH