Easy Installation: The CO detector comes with screws for easy wall or ceiling installation. Powered by 3 x 1.5V AA batteries (not included), it requires no wiring, is portable, and easy to install, without a power outlet. The battery ensures constant monitoring, even during a power outage! The CO detector's battery can be used for approximately 36 months. It is easy to replace and has a long service life. High Accuracy and Reliability: It is equipped with an advanced electrochemical carbon monoxide sensor that accurately detects CO levels in real time. Instant Alert: When the carbon monoxide detector reaches the alarm level, the CO sensor detects CO, the red LED flashes and the blue backlight of the LCD screen turns on. An 85 decibel alarm is emitted. Self-test function and informative LCD display: The device beeps once and the red LED flashes once when powered on. "888" is displayed on the LCD display. Then press the test button to beep and a red LED flashes. Displays real-time CO