Size: 5-5/8" Wide X 3-3/32" 3 Way Protection: Carbon Monoxide, Propane And Natural/Methane GasPlug In With Battery Backup Electrochemical Sensor 3-In-1 Explosive Gas And Carbon Monoxide Alarm With Digital Display And Test ButtonElectrochemical Sensors Are The most Accurate Technology Available For Detecting Carbon MonoxideDigital Display Provides Easy Viewing Of Danger Levels, Current And Peak CO Levels In Your HomeDesigned To Be Wall Mounted So Screen Is VisibleSingle Button Test/Silence For SimplicityLoud 85dB Alarm To Assure Alarm Is HeardEnd Of Life Alarm Notifies You At 60 Months After InstallationPower Source: 120V Outlet With 9V Battery Backup (Included)