The flowing air curtain or barrier prevents {TAIL ~ gas} from exiting {HEAD ~ 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 
The flowing air curtain or barrier prevents { TAIL ~ gas } from exiting { HEAD ~ 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 OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD 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