【How to Use Carbon Monoxide Alarm】Powered by AA batteries, it will automatically turn on after charging, and then enter working mode (the screen will turn off immediately, which is a normal phenomenon). When the concentration value is higher than 30 ppm, the screen will light up and display the value so you can check the PPM value at any time. 【Carbon Monoxide Detector】is equipped with an LCD screen for easy real-time reading of the values (ppm) and audible and visual alarms. When the concentration exceeds a certain level, the alarm sound and the red light will flash. You can quickly and clearly understand the PPM concentration and take appropriate measures to effectively protect your personal and property safety. 【Alarm Self-Test】To test the product's effectiveness, you can perform a self-test by briefly pressing the button once. If the value is not displayed on the screen and an orange light is displayed, it indicates that the battery is fully charged and reminds you to replace the