This device adopts non-dispersive infrared technology (NDIR), with high measurement accuracy, respond quickly, and a resolution of up to 1 ppm that can accurately detect air of Carbon Dioxide (CO2), measuring range 400 - 5000 ppm. The high-definition LED screen allows you to read data faster and more conveniently. There are 4 different color bars on the screen representing the CO2 concentration level: green is healthy, and red is dangerous. This enables quick recognition of the air quality in your surroundings. Please stand the CO2 sensor at the vent for 5-10 minutes for data calibration before using, and allow 35 seconds for the detector to sense the variation if air quality changes. An alarm will sound at 120dB when CO2 in the air exceeds 1,200 PPM, please open the window in time to ventilate or escape the scene if necessary. If the air of CO2 over 1000 PPM, people will feel uncomfortable and work/study efficiency will decrease. In addition, CO2 levels will rise in crowded places,our CO2 meter will remind you in real time for safety with its loud enough sound. With a simple and generous design, its mini size (2.87 x 2.87 x 0.71 inch) makes it easy to carry out, and a built-in 1000 mAh rechargeable battery can continuously work for 8 hours, allowing you to check the air quality anytime and anywhere. This portable CO2 monitor supports USB charging and has a low battery indicator. This mini carbon dioxide monitor is used for grow room, travel, camping, RVs, cars, hotels, parties, wine cellars, kitchens, bedrooms, offices, schools, agricultural planting, indoor , etc. Colour:Black Material:Plastic+Metal Package Contents: 1 x Portable Capnography Monitor 1 Cable Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.