Apparatus 36 includes {HEAD ~ a tube} 37, having a pump 38 at one end and {TAIL ~ gas entry pipes} 39 and 40 shown for convenience as being at the other end 
having
Apparatus 36 includes { HEAD ~ a tube } 37 , having a pump 38 at one end and { TAIL ~ gas entry pipes } 39 and 40 shown for convenience as being at the other end
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH REL OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH