Multifunction CO2 Meter Digital Temp Humidity Tester 3 in 1 Air Quality Monitor Carbon Dioxide PM2.5 Fast Measurement Meter Features  Product Specifications   Detection method for CO2 : Infrared (NDIR)   Detection method for PM: laser scattering   Sampling time: 1.5 seconds   Detection temperature: -10°C to 50°C;   Relative humidity: 20% - 85%   Storage temperature: -10°C to 60°C;   Concentration unit for CO2:PPM   Concentration unit for PM: ug/m3   Power source: Lithium battery with 2000 mAh capacity;   5V DC power charging with micro USB port   Product Size: 267*140*30mm     Product weight: 300g      Product Description      This product is an air quality monitor that detects      Carbon dioxide (CO2),Particulate Matter      (PM2.5),Temperature and Humidity. it combines sensors      real-time monitoring of Carbon dioxide (CO2),      PM2.5,temperature and humidity on its display.      Considerations      Please read the instructions carefully before using this      device.      Please keep the manual handy for quick reference and         troubleshooting        Precautions         Avoid covering the air intake areas during use to avoid         inaccurate measurements.         Avoid use of solvents to clean the product as residual         fumes will skew air quality readings.         Avoid water or other liquids near the product to avoid         electrical damage.         Do not allow unauthorized modifica tion or repair of         this product.         Features:         CO2 indicator   ：         -Big screen display         -Support test variables:Carbon dioxide(CO2),PM2.5,         temperature and humidity         -Support CO2 exceeding alarm         -CO2 alarm threshold can be set         Green: 400ppm to 1000ppm         Yellow: 1001ppm to 2000ppm         Red: 2001ppm to 5000ppm         PM2.5 indicator:         Green: 0~74 ug/m³         Yellow: 75~299 ug/m³             Red: 300~999 ug/m³            Time setting            After turn on, the device auto accesses the interface            which can show CO2 current value, PM2.5,            temperature, humidity, and time. In this state, when you            long-press set button, the digits of hour will flash, press            up button to increase digits or press down button to            decrease digits, and press set button to confirm and            switch to next option.            CO2 alarm threshold Setting            After setting time, the digits of CO2 will flash, then you            can press up button to increase CO2 alarm threshold,            or press down button to decrease CO2 alarm threshold.