Additionally, the housing 12 includes an inlet 15 for receiving {TAIL ~ an assist gas}, which is typically {HEAD ~ air} 
Additionally , the housing 12 includes an inlet 15 for receiving { TAIL ~ an assist gas } , which is typically { HEAD ~ air }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD