{TAIL ~ An air flow sensor} and {HEAD ~ pressure sensor} is positioned to monitor air flow channeled to the mask 
{ TAIL ~ An air flow sensor } and { HEAD ~ pressure sensor } is positioned to monitor air flow channeled to the mask
TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH