Identifying optimal relative humidity and engineering strategies for phase-transition-based aerosol samplers in airborne virus surveillance

Airborne pathogen transmission poses a significant threat to public health, and the selection of appropriate air monitoring techniques for virus aerosols remains a critical challenge in environmental microbiology. Phase transition-based aerosol samplers, which leverage condensation phenomena, have been increasingly employed for on-site monitoring of pathogenic microorganisms. However, the performance of these samplers is depended not only on instrument design but also on operational protocols, working conditions, and environmental parameters. In this study, we investigated the effects of ambient relative humidity (RH) and operating strategies on the performance of a phase transition dry-wall cyclone sampler (PDC-sampler). Using a controlled aerosol chamber, we assessed the aerosol recovery efficiency from an exhalation source and conducted aerosolization experiments with MS2 bacteriophage under controlled RH in a designed chamber. The results indicate that an increase in environmental RH enhances the overall sample volume while concurrently reducing the viral concentration. Moreover, the integration of an engineered flared inlet effectively improves collection (21%) under specific distance from source (3-5cm). By comprehensively evaluating the recovery efficiency of infectious virus aerosols, we determined that an optimal operational RH condition for the PDC-sampler is 60–70%. This study provides an explanatory guidance framework for the design, and characterization of phase-transition aerosol samplers, thereby facilitating improved on-site monitoring of airborne pathogens.