Covid 19 and ventilation

The Italian National Institute of Health on May 25, 2020 issued the "Indications on ventilation / air conditioning systems in non-health community facilities and in domestic environments in relation to the spread of the SARS-Cov2 virus".
The document highlights how adequate ventilation and regular air exchange, in addition to maintaining comfort conditions, are necessary elements to ensure the healthiness of the environments by reducing the concentration of particulates and biological pollutants.
Natural ventilation intrinsically responds to health protection requirements, unlike air conditioning, air conditioning and air treatment systems, which require greater attention in the sanitation of the systems as they are exposed to high risks of contamination.
Electrical ventilation systems cause the formation of jets of air at significant speeds that can interact with the emissions due to breathing, increasing the risk of spreading droplets.
Natural ventilation always provides for the supply of clean external air, while air conditioning systems are frequently based on the recirculation of air inside the rooms, which is therefore potentially contaminated.