First Alert CO410 Battery Operated Electrochemical Carbon Monoxide Alarm with Backlit Digital Display. This carbon monoxide detector uses an electrochemical carbon monoxide sensor. An easy-to-read backlit digital display allows a quick view of current and peak CO levels. This detector is powered by two replaceable AA batteries, offering peace of mind even during power outages. Uses an advanced electrochemical CO sensor to detect elevated carbon monoxide levels. When CO is detected, the carbon monoxide detector sounds an alarm to warn you of the threat. Thanks to the unit's backlit LED display, it's easy to see the current CO concentrations in parts per million, as well as recent peak levels, and the threshold for dangerous levels. The easy-to-read display illuminates when a button is pressed or an alarm is triggered. A remote control can be used to quiet unwanted alarms (remote control sold separately). When carbon monoxide levels rise, the carbon monoxide detector sounds an 85-decibel siren that is designed to wake even the soundest of sleepers. A low-battery alarm alerts you when battery power is running low, and an end-of-life timer lets you know when the device should be replaced. A low battery signal mute quiets the low battery signal for up to eight hours. Each CO detector lasts approximately five years. Simple to set up - insert the two included AA batteries, and the CO detector will start to monitor your space for carbon monoxide. An EZ access battery door allows you to quickly install or remove batteries without having to dismount the alarm. A single button silences the alarm and tests the CO detector.