Room-Based Assessment of Mobile Air Cleaning Devices Using a Bioaerosol Challenge

Abstract

Introduction: The widespread transmission of the SARS-CoV-2 virus has increased scientific and societal interest in air cleaning technologies, and their potential to mitigate the airborne spread of microorganisms. Here we evaluate room scale use of five mobile air cleaning devices. Methods: A selection of air cleaners, containing high efficiency filtration, was tested using an airborne bacteriophage challenge. Assessments of bioaerosol removal efficacy were undertaken using a decay measurement approach over 3 h, with air cleaner performance compared with bioaerosol decay rate without an air cleaner in the sealed test room. Evidence of chemical by-product emission was also checked, as were total particle counts. Results: Bioaerosol reduction, exceeding natural decay, was observed for all air cleaners. Reductions ranged between devices from <2-log per m 3 room air for the least effective, to a >5-log reduction for the most efficacious systems. One system generated detectable ozone within the sealed test room, but ozone was undetectable when the system was run in a normally ventilated room. Total particulate air removal trends aligned with measured airborne bacteriophage decline. Discussion: Air cleaner performance differed, and this could relate to individual air cleaner flow specifications as well as test room conditions, such as air mixing during testing. However, measurable reductions in bioaerosols, beyond natural airborne decay rate, were observed. Conclusion: Under the described test conditions, air cleaners containing high efficiency filtration significantly reduced bioaerosol levels. The best performing air cleaners could be investigated further with improved assay sensitivity, to enable measurement of lower residual levels of bioaerosols.

A SARS-CoV-2 outbreak in a plastics manufacturing plant

“…This finding aligns with recent models that suggest inadequate ventilation may contribute to both far-field and within-room inhalation transmission of SARS-CoV-2 [ 8 ]. Although it is well-demonstrated that effective ventilation can reduce risk of far-field inhalation transmission, settings where there is no mechanical ventilation, as is the case for this workplace, and natural ventilation cannot reliably supply sufficient fresh air, suitable portable air cleaning interventions such as HEPA (high-efficiency particular air) filters and/or UV (ultraviolet) radiation air disinfection could be used to remove or deactivate potential viruses from the air [ 9 , 10 ]. Evidence suggests a reduction in the detection of SARS-CoV-2 in air samples following the use of HEPA air filtration [ 11 ], as well as the augmentation of airborne viral elimination when combined with primary mechanical ventilation methods [ 12 ].…”