Carbon dioxide in classrooms

Carbon dioxide (CO2) is exhaled by humans as a metabolic product. It is therefore often used as an "indicator gas" for indoor air quality: the higher the CO2 concentration in the air, the poorer the air quality. The CO2 concentration can rise very quickly, especially in rooms with many people present (school classes, meeting rooms). As CO2 in higher concentrations can lead to tiredness, poor concentration and other mood disorders, the gas must be removed from the room by appropriate ventilation.

Guide values for the COindoor air concentration

In Germany, the Committee for Indoor Guideline Values (formerly known as the ad hoc working group) has derived health and hygiene guideline values for the CO2 indoor air concentration. A CO2 concentration below 1000 ppm is considered harmless. The 1000-2000 ppm range is to be assessed as hygienically conspicuous and ventilation measures must be intensified. At a CO2 concentration above 2000 ppm, the indoor air quality is hygienically unacceptable. Room ventilation options must therefore be reviewed and improved.

CO2 calculator

The calculator used here for the CO2 concentration is based on the assumption that the room is very well ventilated at the start of the analysis and that the outdoor air concentration of carbon dioxide therefore corresponds to that indoors. For other initial conditions, the values given below can be used as a guide. In general, the use of a "ventilation traffic light" in the classroom area is recommended.


Room area in m2:
Number of people:


Some values cannot be calculated for extreme conditions. These are marked with "n.d." marked.