Abstract- The novel SARS-CoV-2 virus which causes the COVID-19 disease, is mainly transmitted through contact with infected persons according to WHO. Breathing, as well as coughing and sneezing releases tiny infectious droplets into the air which potentially contaminate surrounding surfaces and of course the air in the immediate surrounding. These droplets, so called aerosols, can be of varying sizes, from 1 to over 10 µm (micron or micrometre, 1 micron equates to 0.001 mm). It is assumed by experts that viruses do not fly occasionally in the air but are always enclosed in droplets or attached to other particulate matter. This raises the question in which way ventilation and air-conditioning systems play a role in the transmission or containment of epidemic diseases like COVID-19. Maintaining a healthy indoor air quality thus becomes a general, basic – yet extremely important – necessity. While this is true at all times, it’s imperative in times of a wider health crisis to avoid not only the direct spread of a virus, but to support peoples immune systems to withstand more serious impacts by an aggressive disease and thus reducing pressure on a healthcare system fighting against overload.