A gas escape and monitor pipe 22 at the lowest level of {HEAD ~ the gas} in {TAIL ~ 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 
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A gas escape and monitor pipe 22 at the lowest level of { HEAD ~ the gas } in { TAIL ~ 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
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