Calculation of Ventilation Rate

To calculate the estimated ventilation ratio (how many times the total amount of air in a given space is exchanged in one hour), it is necessary to specify the concentration of CO₂ in the outdoor air; the default value is set to 420 ppm. In some locations, outdoor CO₂ concentrations may be higher.

This link provides the latest results of long-term monitoring of CO₂ concentration in outdoor air at the Mauna Loa Observatory on the island of Hawaii in the middle of the Pacific Ocean. This site has the longest historical monitoring of CO₂ concentration. After that, you need to enter the volume of the monitored space, the number of occupants, select the type of activity, enter the indoor CO₂ concentration, and press the Calculate button.