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