The AirBoss Sentinel combines a pressure gauge, IPass, time-to-whistle, and data logging into one unit. The AirBoss Sentinel calculates air supply time based upon actual air usage and first warns when 50% of the air is used. The AirBoss Sentinel provides a second independent visual alarm and is compatible with AirBoss Evolution and AirBoss PSS100 SCBA's. Please call one of our sales representatives for additional information.