{HEAD ~ A sensor} is provided for monitoring air pressure, with the sensor issuing a pressure detection signal that is greater or lower than a preferred range of air pressure for {TAIL ~ air flow} transmitted to the mask 
{ HEAD ~ A sensor } is provided for monitoring air pressure , with the sensor issuing a pressure detection signal that is greater or lower than a preferred range of air pressure for { TAIL ~ air flow } transmitted to the mask
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH