describe This type of smoke and carbon monoxide detector uses electrochemical carbon monoxide sensors, which are the most accurate carbon monoxide sensors currently available. Compared with ordinary electrochemical technology, the latter technology has higher accuracy, lower power consumption and longer service life. The battery smoke detector is suitable for indoor places such as villas, factories, shopping malls, warehouses, office buildings, etc. function -New 2-in-1 smoke and carbon monoxide detectors. High-precision electrochemical sensor (the most accurate CO sensor). Infrared photoelectric sensor (the best sensor for detecting smoke while minimizing false alarms) -Low power consumption design: After installing 3 batteries (3 x 1.5V AA batteries, the package does not include batteries), you can hear the DI sound and start working normally after 2 minutes. During operation, it does not display any power-saving design. Long standby time and low power consumption. -Loud alarm: