{TAIL ~ The curtain} or {HEAD ~ barrier} is formed by a region of flowing conditioned air directed across the opening 
{ TAIL ~ The curtain } or { HEAD ~ barrier } is formed by a region of flowing conditioned air directed across the opening
TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH