"Air Checker 7722" CO2, Temp. & RH detector could measure the indoor air quality (IAQ) index, including the CO2 concentration, CO2 level, air temperature, dew point, wet bulb temperature and humidity. And it can be calibrated easily in the fresh air.
Poor indoor air quaintly is considered unhealthy because it causes tiredness, loss of ability to concentrate, and even illness (ex: sick building syndrome). IAQ monitoring and survey, especially on CO2 level and air ventilation become widely applied in public areas such as office, classroom, factory, hospital, work space, residential, commercial building and hotels. It is also suggested in regulations of industrial hygiene in some countries.