In the open position which is shown, {HEAD ~ air} can flow through {TAIL ~ the ventilation opening} 14 in the housing 12 past the closing part 16 between the covers 21 and the latching means 18, 19 
In the open position which is shown , { HEAD ~ air } can flow through { TAIL ~ the ventilation opening } 14 in the housing 12 past the closing part 16 between the covers 21 and the latching means 18 , 19
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH 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