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