An energy-efficient heat-driven technology for airborne pathogen inactivation: integration of two-stage HVAC filtration with thermal disinfection

• Proposed a thermal disinfection method for two-stage HVAC filters. • System tested in ASHRAE 52.2-compliant closed-loop aerosol wind tunnel. • Theoretical efficiency correlation deviates from experiments during disinfection. • Disinfection mode increases pressure drop and alters particle removal. • Reducing inter-filter spacing minimizes energy use without loss in performance. Air filters are widely used in HVAC systems to control transmission of airborne microorganisms. However, their application is associated with frequent maintenance, accumulation and release of bioaerosols. To address these issues, the present study proposes a novel thermal disinfection approach integrated into a two-stage filtration system comprising a MERV 8 pre-filter and either MERV 11 or MERV 13 main filter. To maintain continuous airflow, the system employs two side-by-side units with the same filters sequentially disinfected via forced convection heating while maintaining continuous filtration. A closed-loop aerosol wind tunnel, based on the ASHRAE 52.2 standard, was implemented to evaluate the filtration efficiency and pressure drop of the system at various configurations and operating modes, including normal operation (both units open) and a disinfection period (one unit closed). Moreover, a heat transfer setup was developed to measure the required time and energy consumption for meeting the literature-based thermal inactivation criteria (10 min exposure to 65 °C) across three inter-filter distances. A comparison of the theoretical correlation for estimating the overall filtration efficiency of multi-stage systems with experimental results confirmed good agreement in normal operation, with some deviations during the disinfection period due to flow redistribution. Furthermore, changing the inter-filter distance has relatively minor impacts on the overall filtration efficiency and pressure drop compared to its effect on the disinfection process. Consequently, the energy performance of the disinfection system should be considered the primary criterion when determining the optimal distance between the pre-filter and the main filter.