Long-term solution Compact and affordable, the Gas Alert Extreme reliably monitors for any single gas hazard within its wide range of available toxic gas models. With easy on/off operation, this single gas detector offers extended longevity with a two year field-replaceable battery and sensor. A wide range of tamperproof user options and multi-language display make the Gas Alert Extreme an ideal solution for a variety of applications; plus, datalogging is now standard on all units. Calibration is a simple automatic procedure and is compatible with BW? MicroDock II automatic test and calibration system.