Remarks on the air recirculation in HVAC systems during the SARS-CoV-2 outbreak: the case of all-air ducted plants

The SARS-CoV-2 pandemic has aroused great interest in the HVAC community, both as regards to the design of new systems and for the management and operation strategies of the existing ones. The risk management plays a key role in all-air systems based on air recirculation among segregated spaces. Following an analyti- cal approach, this paper assesses the infection risk in several HVAC systems layouts. It takes into account the role of air renewal and recirculation and the gain made possible by means of virus charge removal or deactivation (through filtration or other technologies such as UV-C irradiation, ionisation …), with special regard to the management of airflows that depends on the chosen plant layout.