The triplett model gsm200 desktop indoor air quality co2 monitor simultaneously displays co2, temperature, relative humidity, time and date and can be used to measure air quality in office buildings, schools, exhibition halls, shopping malls, meeting rooms, fitness centers, restaurants and other public places. It has 3 status indicators good/normal/poor that change with co2 concentration and user programmable audible/visual co2 alarms good default 800ppm, poor default 1200ppm with disable to alert you when safe co2 levels have been exceeded. The sensor incorporates ndir non-dispersive infrared waveguide technology and has a built-in co2 automatic baseline calibration for long term drift compensation. Min/max function records the highest and lowest readings for co2, temperature and humidity over time and data hold can freeze the reading on the display for easy viewing. Temperature readings are f/c selectable. 1-year warranty. Includes ac adapter.