The firestop prevents fire and {HEAD ~ smoke} from moving through {TAIL ~ the inner passageways} of the pipes of a drainage system by blocking the inner passageway of the pipes with a fire resistant plug  
The firestop prevents fire and { HEAD ~ smoke } from moving through { TAIL ~ the inner passageways } of the pipes of a drainage system by blocking the inner passageway of the pipes with a fire resistant plug
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH