FIG 4A illustrates a normal operating condition of the elongated conduit body prior to {HEAD ~ the detection} of {TAIL ~ any ignited flammable gases} 
of
FIG 4A illustrates a normal operating condition of the elongated conduit body prior to { HEAD ~ the detection } of { TAIL ~ any ignited flammable gases }
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 TAIL