TVOC sensor: The design of co2 detector meter with TVOC sensor to monitor CO2 value, temperature and air humidity to keep your health environment, we recommend you to use the USB charger Real-time monitoring and automatic alarm: The carbon dioxide monitor can detect air in real time and with 1999 CO2 concentration. Four warning lights flash at the same time for alarm Easy to read: co2 sensor with smart color display and clear numbers. And when the CO2 concentration 1600-1999 of the red light comes on and alert Wide Application: Portable CO2 monitor with compact design, suitable for air quality monitoring at home, schools, office buildings, hospitals, restaurants, shopping malls, factories , hotels,laboratories, etc Why you need it: Perfect gift for your Valentine's Day gifts for him/her/kids, with the air quality monitor, you can definitely know what your environment is like and improve it depends onactual situation.