The First Alert CO615 Plug-In Carbon Monoxide Detector helps protect your family with an electrochemical sensor, an 85-decibel alarm, and an easy-read digital display. It plugs into any standard outlet with no additional mounting necessary. It also includes a battery backup, so CO is monitored even if there's a power failure. The Peak Level feature displays the highest concentration of carbon monoxide measured since the unit was last reset. One button silences any nuisance alarms, and also tests detector functions. And an end-of-life signal enhances your safety by letting you know when it's time to replace the unit. Keep your family safer by installing units on multiple levels and in each bedroom.