A check valve in the vent inhibits the flow of fugitive gases to the vent and allows {HEAD ~ the escape} of {TAIL ~ the fugitive gases} to the vent if the pressure of the fugitive gases exceeds a predetermined value 
of
A check valve in the vent inhibits the flow of fugitive gases to the vent and allows { HEAD ~ the escape } of { TAIL ~ the fugitive gases } to the vent if the pressure of the fugitive gases exceeds a predetermined value
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH