Features: This CO2 detector can accurately and quickly test CO2 levels indoors to protect your health. Also, provides real-time monitoring of indoor temperature and humidity. Using infrared technology, high measurement accuracy, fast response, resolution up to 1ppm, can accurately detect CO2 in the air, the measurement range up to 400-5000ppm. This indoor air carbon dioxide meter has 4-color LED indicators as an air quality warning. Different color indicators will flash according to CO2 content, which makes air quality more intuitive. 1200mAh rechargeable battery provides 240-360 minutes of standby time and can be recharged via Type-C charging port. 2.8 inch LCD screen with backlight display, clear and soft display, thus making reading clear. Portable size, easy to carry around. Simple operation. No need to calibrate after starting up, work and detect automatically. It can be used at various occasions such as office, car, school, hotel, greenhouse vegetables, production warehouses, raw materials processing, etc. Carbon Dioxide Instructions: 0~799ppm: green light flashes 800~1199ppm: yellow light flashes 1200~1599ppm: orange light flashes 1600~1999ppm red light flashes Above 1999ppm, four-color lights flash