High Accuracy Infrared Sensor: The CO2 detector uses the most advanced infrared sensor, accurately and quickly detects the concentration of CO2, also measures the temperature and humidity in the ambient air in real time. Large screen Three-Color LCD and Alarm: Three LCD colors indicate different CO2 ranges (400-1000ppm: green, 1000-3000ppm: yellow, 3000-5000ppm: red). When the CO2 concentration is 1000-3000ppm, the carbon dioxide detector will sound an alarm every 2; when the CO2 concentration is 3000-5000ppm, the carbon dioxide detector will sound an alarm every 1s.[Temporarily mute or turn off the sound function] The CO2 level is 1000-5000ppm, the CO2 tester will sound . When you know this potential danger exists, you can press the power button to mute the sound temporarily. If you don't need this carbon dioxide (CO2) alarm sound, you can directly enter the setting button to turn off the sound. Usage: widely used in home, bedroom, office, classroom, car , garden shed, warehouse, etc. Digital display and large LCD screen, easy to read, real-time monitoring, allowing you to take action in a timely manner. Easy to carry: lightweight and small size design, easy to carry. Can be placed anywhere: schools, offices, bars and restaurants, homes, cars, etc. Easy to charge with USB cable.