Viruses can be transmitted via aerosols. The risk of transmission should be reduced as far as possible. Opinions vary, however, on how to achieve this. Some believe that it is sufficient to increase the air exchange rate of rooms. Others call for installation of highly efficient air purifiers in all classrooms, conference rooms, or doctor’s waiting rooms not connected to an appropriately designed central air filtration system, as a general rule.

In the face of Covid-19 and future challenges decision makers in the public and private sectors need objective guidance for specifying requirements to be met by individual air hygiene concepts. More reliable data is required. Sole measurement of the CO2 level is insufficient for optimal design of ventilation concepts and determination of required air filtration capacity, which complicates the task further. Virus carrying aerosol particles are so small that most measuring devices cant detect them.

Indoor spaces vary considerably regarding dimensions, furnishing, technical facilities and uses, as well as occupancy needs. This calls for individual on-site assessment by experts in this field. With appropriate measurement technology, potentially infectious aerosols can be reliably determined – the basis for developing reduction concepts.