First Alert Plug-In Battery Back-Up Carbon Monoxide Alarm Plug-in CO carbon monoxide alarm with battery back-up utilizes an electrochemical carbon monoxide sensor to accurately and effectively warn you of elevated CO levels. The plug-in design and included battery back-up mean your space can be continuously monitored for dangerous carbon monoxide gas, even during power outages. Battery life varies according to use and application. Simply plug the alarm into a 120-volt outlet, and the personal carbon monoxide detector is ready to go. When CO levels rise above a safe threshold, a loud 85-decibel alarm alerts you to the threat. Designed for simple use, the CO detector has just one button that silences or tests the unit, as well as an end-of-life timer that lets you know when it is time to replace the device. Type Plug-In, Voltage 120V, Battery Life Varies According To Battery Life, Sensor Type Electrochemical, Dimensions 5 In. W. x 1-2/5 In. H. x 3-2/5 In. L., Battery Back-Up Yes, Alarm Type Carbon Monoxide, Decibel Level 85dB, Battery Type 9V Battery, Batteries Included Yes, Color White, UL Listed Yes, Warranty 7-Year Limited, Pkg Qty 1, Package Type Clamshell