Plug-in carbon monoxide detector with 9V battery backup ensures ongoing protection during outages, sounding a powerful 85 dB alarm upon detecting hazardous CO levels. It employs electrochemical sensor technology for dependable and precise detection, plus a convenient test/silence button. The slim unit fits any standard 120V outlet, allowing versatile positioning around the house. | First Alert | | Plug-In w/Battery Back-up Electrochemical Carbon Monoxide Detector | Best Buy