The flowing air curtain or {HEAD ~ barrier} prevents {TAIL ~ gas} from exiting the oven interior when the door is opened, and it also serves to replace or replenish any conditioned air which happens to escape from the oven interior 
prevents
The flowing air curtain or { HEAD ~ barrier } prevents { TAIL ~ gas } from exiting the oven interior when the door is opened , and it also serves to replace or replenish any conditioned air which happens to escape from the oven interior
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL 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 OTH OTH OTH OTH OTH OTH OTH OTH OTH