d) measuring {TAIL ~ the flow} of air from {HEAD ~ said second compartment} through said outlet means; and 
d ) measuring { TAIL ~ the flow } of air from { HEAD ~ said second compartment } through said outlet means ; and
OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH