Air is taken in via an enclosure front face from outside {HEAD ~ the enclosure} due to the cooling fans rotation, flows through {TAIL ~ the interior space} of the enclosure, and passes through the backboard 
Air is taken in via an enclosure front face from outside { HEAD ~ the enclosure } due to the cooling fans rotation , flows through { TAIL ~ the interior space } of the enclosure , and passes through the backboard
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH