{HEAD ~ The gas} and {TAIL ~ vapor} evolved in these zones passes upwardly through the vents 94 into the vapor collection region 89 and is removed 
{ HEAD ~ The gas } and { TAIL ~ vapor } evolved in these zones passes upwardly through the vents 94 into the vapor collection region 89 and is removed
HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH