Wind tunnel‐based testing of a photoelectrochemical oxidative filter‐based air purification unit in coronavirus and influenza aerosol removal and inactivation

Abstract

Recirculating air purification technologies are employed as potential means of reducing exposure to aerosol particles and airborne viruses. Toward improved testing of recirculating air purification units, we developed and applied a medium‐scale single‐pass wind tunnel test to examine the size‐dependent collection of particles and the collection and inactivation of viable bovine coronavirus (BCoV, a betacoronavirus), porcine respiratory coronavirus (PRCV, an alphacoronavirus), and influenza A virus (IAV), by a commercial air purification unit. The tested unit, the Molekule Air Mini, incorporates a MERV 16 filter as well as a photoelectrochemical oxidating layer. It was found to have a collection efficiency above 95.8% for all tested particle diameters and flow rates, with collection efficiencies above 99% for supermicrometer particles with the minimum collection efficiency for particles smaller than 100 nm. For all three tested viruses, the physical tracer‐based log reduction was near 2.0 (99% removal). Conversely, the viable virus log reductions were found to be near 4.0 for IAV, 3.0 for BCoV, and 2.5 for PRCV, suggesting additional inactivation in a virus family‐ and genus‐specific manner. In total, this work describes a suite of test methods which can be used to rigorously evaluate the efficacy of recirculating air purification technologies.

Photoelectrochemical oxidation assisted air purifiers; perspective as potential tools to control indoor SARS-CoV-2 Exposure

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Fig. 8 The scenario of closed premises with contaminated air (A) , a wind tunnel system utilized for Recirculating air purification technologies (B) , summary performance outcomes of Molecule air purification technology (C) , and RT-qPCR based viability evaluation of BCoV, PRCV, & influenzas A virus (IAV) tested with reference to performance Molecule air purifiers (D) [ 22 ].

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“…Based on the principle of recirculating air purification phenomena, a wind-tunnel ( Fig. 8 C) based performance of PECO technology was demonstrated to evaluate the viability of bovine coronavirus (BCoV, a beta coronavirus), porcine respiratory coronavirus (PRCV, an alphacoronavirus), and influenza A virus (IAV) [22] , as shown in Fig. 8 D .…”

“…The hospital central HVAC system and MERV-rated filters is a generalized approach toreduce bacteria and fungi in the air, but other airborne microbes and toxins can exist in localized indoor environment at very high levels. This may be due to the pathogens or pollutants carried by the patient or hospital workers, those disturbed by movement in the room, or otherwise those that are not effectively filtered by the central HVAC system [ 21 , 22 ]. Patients and hospital workers may be at a higher risk due to pathogenic complications in the air.…”

“…Indoor air quality is always a concern to maintain according to international standards but not well highlighted due to lack of awareness and widespread technology. Recent viral infection outbreaks (COVID-19 pandemic) not only forced health agencies globally to develop better medical infrastructure and new policies to deal with infectious diseases but also made the general population understand the value of clean air [21] , [22] , [23] . As a result, the need for virus-free indoor air to avoid virus exposure raised the demand of investigating new technologies which can clean the air in reduced form factors, i.e., with more advantages, affordability, and acceptability.…”

An experimental method for efficiently evaluating the size-resolved sampling efficiency of liquid-absorption aerosol samplers

“…In addition, a phenomenon of large particle deposition in the test chamber was observed, that may be the reason for the relatively large variation in aerosol concentrations for particles above 10 µm, and also leads to a narrow aerodynamic particle size range of 0.6–16.9 µm for samples collected in the AtoH sampling test while ATD aerosols with aerodynamic particle size of 0.6—27 µm are generated. In this case, an aerosol wind tunnel would be more suitable for sampling performance tests of large particles, because of its stability and uniformity for a wide diameter range of aerosols in testing 31 , 48 , 49 . Nevertheless, the detection size range of both the AtoA and AtoH sampling tests in this study are wide enough for testing the respirable and thoracic samplers 50 , 51 .…”