Plug-in CO (carbon monoxide) alarm featuring battery back-up and backlit digital display. Uses an electrochemical carbon monoxide sensor， the most accurate CO detection technology available， to detect the CO you can't see， smell， or taste in the air. Easy-to-read backlit digital display allows a quick view of current and peak CO levels. Plugs into any wall outlet and includes a battery back-up for detection even during power outages. EZ access battery door allows you to change batteries without having to dismount the alarm. Battery life varies according to use and application. An 85-decibel horn sounds if carbon monoxide levels are too high， and a test/silence button silences the alarm and allows you to test its functionality. Meets UL2034 standards.