At home, at work, in public transport: People in Europe spend up to 90% of their time indoors. Depending on their age and activity, every single person breathes in 12 to 24 kg or 10 to 20 m³ of air per day. However, when exhaling, we humans breathe out a significant amount of CO2. So you could say we become CO2 producers ourselves, and, with that, we are the main influencers of the air quality in our indoor spaces. 

How to assess and maintain the indoor air quality is being discussed all over the world these days. The main reason for this is that crowds of people in closed rooms are currently only allowed if great efforts are made in terms of hygienic indoor air conditions. Therefore, solutions are needed to improve the indoor air quality and to reduce the risk of virus infection by aerosols in the air. A very promising approach can be a decentralised room ventilation system, depending on the CO2 concentration.