The First Alert Ten-Year 2-in-1 photoelectric smoke detector with carbon monoxide alarm features our new slim design and maximum protection. It's protection at its finest and lasts a full 10 years without the hassle and expense of twice a year battery changes. The sleek new design is half the size of standard alarms and looks elegant on your wall or ceiling, blending in easily with decor. Our patented smoke entry system allows for a direct path to the smoke sensor, helping to minimize nuisance alarms that often come from cooking smoke or shower steam. In addition, this combination alarm uses photoelectric smoke sensing technology that detects smoke particles most commonly produced by smoldering fires and a highly accurate electrochemical sensor to detect carbon monoxide gas. Loud 85 dB alarm sounds if hazard is detected. Single test/silence button mutes unnecessary alarms and tests fiction. Simple twist/lock mounting bracket makes it quick and easy to install your First Alert smoke alarms. End of life timer sounds when it's time to replace your alarm. Backed by 10 year limited warranty from First Alert.