After a predetermined time the valve in {HEAD ~ the closed system} is opened allowing {TAIL ~ the fluids} therein to flow freely 
After a predetermined time the valve in { HEAD ~ the closed system } is opened allowing { TAIL ~ the fluids } therein to flow freely
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH