The method also includes {HEAD ~ the step} of sensing a parameter representative of {TAIL ~ air flow} through the hole 
The method also includes { HEAD ~ the step } of sensing a parameter representative of { TAIL ~ air flow } through the hole
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH