The knowledge about nanoaerosols, their potential health effects, their measurement, limitation and administrative-legal treatment has been developed in the last 3 decades in connection with the exhaust gas cleaning of the combustion engines. Nanofiltration, which has thus become known, almost completely eliminates nanoparticles with filters of high durability, high specific filtration areas, and reasonable costs. On the occasion of the Covid pandemic, NanoCleanAir experimentally proved that the viruses in an automotive filter substrate are separated as well as the combustion particles and are also deactivated. To minimize cross exchange of infectious aerosol, new attention must be paid to flow management in ventilated spaces. Digitized flow analysis has also received significant inspiration from engine technology in the past. This paper provides information on some basic investigations and gives valuable advice based on the experimental and numerical results of a retrofitted classroom.