Modelling and simulation of a single-zone highly occupied indoor space to minimize aerosol exposure and energy consumption of HVAC systems

The importance of airborne transmission of COVID-19 in an indoor environment is now widely recognized, and it has drawn worldwide attention from both government organizations and researchers. Also, highly occupied indoor spaces such as restaurants, bars, and pubs have been the primarily affected service sectors due to the enforced lockdown measures. In this paper, the relative reduction in virus-laden aerosol exposure in a single-zone highly occupied space due to (i) the operation of HVAC systems and (ii) usage of non-HVAC control measures are investigated by using a recently developed web-based simulation tool. This tool was used to model the release of bio-aerosols in a highly occupied indoor space (i.e., bar or pub) with three different types of HVAC systems (central air handling system, dedicated outdoor air system, and wall unit system). Besides, the non-HVAC control measures were considered, including wearing face masks and use of room air cleaners. The occupant exposure was evaluated for 1 μm aerosols by which SARS-CoV-2 are transported within the indoor space. The exposure was estimated for 3 hrs./day of continuous exposure to a continuous source. The mitigation effects of different types of air filters in the recirculation line of the HVAC systems, ventilation using outdoor air based on the Spanish Thermal Building Regulations (RITE) and use of portable air cleaners (PACs) were investigated. The combined effect of ventilation, recirculated air filtration, and use of the PAC was evaluated in the reduction of aerosol exposure to uninfected occupants with and without wearing face masks. The energy consumption related to the applied control measures was also estimated for each type of HVAC system. In summary, the results of this study contribute to the selection of control options depending on the type of existing HVAC systems and reduced energy consumption.