[High Sensitivity and Quick Response]Built-in carbon monoxide detection chip and electrochemical sensor, which are enough to detect the odorless invisible and deadly carbon monoxide in the air, respond quickly in the event of a fire, and save your life in the first time. [Safe and Visible]Carbon Monoxide Alarm Detector Optional 3-digit LCD display, Err is displayed on the LCD to indicate that the device is malfunctioning. Lb on the LCS means the battery is low and needs to be replaced. 999ppm on LCD indicates CO levels over 999ppm and Loud 85dB alarm with LED flash In alarm mode, protect your family from carbon monoxide for life-saving safety. [ALARM WARNING]When a dangerous level of carbon monoxide is detected, the red LED will flash and sound a loud alarm pattern - a loud 85 decibel alarm with LED flash. [Easy installation and wide range of applications]Co detector comes with installation accessories, just need to drill holes in the right place to complete; it can be used in bedrooms, kitchens, living rooms and any other areas with fire danger to install smoke detectors and Carbon monoxide alarm. [Energy Saving]3*1.5V AA battery powered CO detector battery not included, low current consumption, super long standby time.