Factors Affecting Reduction of Infectious Aerosols by Far-UVC and Portable HEPA Air Cleaners

Technologies that can reduce concentrations of airborne microorganisms through either particle capture or inactivation are important tools for reducing the risk of disease transmission and improving overall indoor air quality. The effectiveness of these technologies is tested in different ways, and as a result, it is challenging to compare results and optimize their use in applied settings. In this study, experiments were conducted in a large bioaerosol chamber to evaluate the efficacy of far-UVC and portable HEPA air cleaners against the bacteriophage MS2 as a surrogate for human viral pathogens. For both technologies, changing the media used to aerosolize the microorganism from deionized water to a simulated saliva doubled effectiveness metrics (both log₁₀ reductions and clean air delivery rates). Because reductions did not follow first order, log-linear dynamics, using different segments of the test period to calculate efficacy also significantly impacted reported performance. Evidence shown here indicates that both microbiological and particle dynamics likely play a role in impacting test outcomes under current methods, and more research is needed to improve repeatable and reliable standardized approaches for determining technology performance against infectious aerosols.