The First Alert Dual-Power Carbon Monoxide Plug-In Alarm lets you monitor carbon monoxide levels nearly anywhere. Simply plug this personal carbon monoxide detector into any standard outlet, and the backlit digital display will show the level of carbon monoxide in the room. A battery backup sustains the CO detector in the event of a power outage, and a power level indicator on the display and end-of-life timer let you know when the device needs to be replaced.