All studies have shown that the CO2 concentration is a good indicator of indoor air pollution. So that the CO2 concentration made it possible to judge the quality of the ventilation of a room.
COVID-19 is transmitted primarily through aerosols (particles in the air), much more than through contact with surfaces. Aerosol particles from contaminated people are emitted, through exhalation, speaking or coughing. While wearing a mask reduces the circulation of these aerosols, a certain quantity of aerosols is still dissipated into the indoor air.
The Technical University of Berlin (TU Berlin) has demonstrated the direct relationship between the concentration of CO2 and the concentration of aerosols potentially infected with COVID-19, in closed spaces.
The concentration of CO2, and therefore indoor air pollution, is directly linked to the intensity of human activity (number of people, type of activity) that takes place there, and the quality of ventilation.
The following graph, showing the measurements made by the Technical University of Berlin, shows the evolution, over time, of the concentration of CO2 and VIRUS, depending on the quality of the ventilation.
It is therefore no coincidence that the various governments strongly recommend to ventilate regularly during this period of the COVID19 pandemic, and to be equipped with a CO2 measurement sensor. Ventilation can either be manual (open the windows – create a draft with the outside), or mechanical (by increasing the air circulation of a ventilation or air conditioning).
Note that in most countries, there is already a regulation that limits the CO2 concentration in indoor spaces, to limit increase the concentration, limit respiratory problems of people at risk, and reduce contagion). By way of example, this CO2 concentration limit is 950 ppm in Belgium, or even 1000 ppm in France.