{HEAD ~ An oxidizing gas}, preferably pressurized air, is periodically fed into the exhaust line by {TAIL ~ an oxidizing gas line} for cleaning the drain line and the pressure controlling aperture therein by oxidizing the magnesium 
is periodically fed by
{ HEAD ~ An oxidizing gas } , preferably pressurized air , is periodically fed into the exhaust line by { TAIL ~ an oxidizing gas line } for cleaning the drain line and the pressure controlling aperture therein by oxidizing the magnesium
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH REL REL REL OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH