The First Alert CO615 carbon monoxide alarm uses an electrochemical sensor the most accurate technology available. 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. The test/silence button silences the alarm and allows you to test its functionality. This CO detector also features a battery backup that allows for continuous monitoring, even in the event of a power failure. The simple, user friendly design makes this CO detector easy to setup and operate, and it features an end-of-life warning that lets you know when it is time to replace the unit.