The First Alert CO615 Plug-In Carbon Monoxide Alarm with Battery Backup and Backlit Digital Display will notify you of any potentially harmful carbon monoxide leakage. The most precise CO detection device now in use is an electrochemical carbon monoxide sensor, which this detector employs to identify the CO in the air that is invisible to the human senses of taste, smell, or scent. The current and peak CO levels can be quickly viewed on an easy-to-read backlit digital display. This device has a battery backup for detection even in the event of a power outage, and it plugs into any wall socket. You can replace the batteries in an alarm without taking it apart thanks to an EZ access battery door. When carbon monoxide levels are too high, an 85 dB horn blasts, and a test/silence button lets you test the air.