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