Apparatus and method for stopping {TAIL ~ the propagation} of {HEAD ~ ignited flammable gas} in a conduit 
Apparatus and method for stopping { TAIL ~ the propagation } of { HEAD ~ ignited flammable gas } in a conduit
OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH