There is a protective film on the product screen No need to calibrate after starting up , work and detect automatically Instructions 1, Press and hold the "on-off" key on the right for 3 seconds to turn on and turn off , then it will display the current air quality parameters . 2, CO2 Detector : It displays the current CO2 data ,as well as the temperature and humidity data ,the colored ring will change according to the CO2 conten 3, It is a simple operation that you can long press the " on-off " key on the right side for 3 seconds to turn on and off . 4, The USB can be charged by plugging in a 5V power supply .The battery icon flashes in the charging state ,and it stops when it is full . if the display is full but still flashing .it means that the charging is not saturated .Please wait for a while . Technical Indicators 1. TVOC Detection Range : 0-2 ppm 2. Applicable temperature: -1 ~ 70 3. Display mode: LED screen + backlight 4. Standby time: about 300-420 minutes,Battery capacity 1200 MHA 5. CO2 Detection range: 400-5000 ppm 6. CO2 Detection Sensitivity : 1 ppm 7. Temp Measurement Range : 0-50 8. Temp Measurement Accuracy : +-1 9. Humidity Measurement Range : 0%-99%RH 10. Humidity Measurement Accuracy: +-2%RH 11. Sensor: TVOC sensor 12. Charging standard: 5V-1A