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