CO alarm - 1 yr batt with display _Effective protection against carbon monoxide (CO): this detector, with a range of between 20 and 40 m_, is equipped with an electrochemical sensor capable of detecting CO in the air, even in small quantities (about 27ppm) _Digital screen: the screen of the carbon monoxide detector indicates the concentration of CO (PPM) and displays any malfunctions: batteries or device at the end of their life, incorrect installation _Test button: make sure your device is working properly by testing it regularly (once a month) _10 Year Sensor & Replaceable Batteries: The sensor in this CO detector has a lifespan of 10 years. The detector is powered by 3 included AA batteries.