BKidde KN-COEG-3 Plug-In Combination Carbon Monoxide Detector and Gas Alarm with Bonus Ionization Smoke Alarm Battery Backup ReviewbP PP Kidde KN-COEG-3 Plug-In Combination Carbon Monoxide Detector and Gas Alarm with Bonus Ionization Smoke Alarm Battery Backup PCombination carbon monoxide and explosive gas alarm includes a 9 Volt battery backupPEquipped with a peak level button, pressing the button you can see the peak CO level recorded by the alarm since it was last reset or unpluggedPContinuous digital display shows you the level of carbon monoxide (if any) the unit is sensing as well as if gas is presentP