Abstract
Transmission of SARS-CoV-2 by aerosols has played a significant role in the rapid spread of COVID-19 across the globe. Indoor environments with inadequate ventilation pose a serious infection risk. Whilst vaccines suppress transmission, they are not 100% effective and the risk from variants and new viruses always remains. Consequently, many efforts have focused on ways to disinfect air. One such method involves use of minimally hazardous 222 nm far-UVC light. Whilst a small number of controlled experimental studies have been conducted, determining the efficacy of this approach is difficult because chamber or room geometry, and the air flow within them, influences both far-UVC illumination and aerosol dwell times. Fortunately, computational multiphysics modelling allows the inadequacy of dose-averaged assessment of viral inactivation to be overcome in these complex situations. This article presents the first validation of the WYVERN radiation-CFD code for far-UVC air-disinfection against survival fraction measurements, and the first measurement-informed modelling approach to estimating far-UVC susceptibility of viruses in air. As well as demonstrating the reliability of the code, at circa 70% higher, our findings indicate that aerosolized human coronaviruses are significantly more susceptible to far-UVC than previously thought.
Highlights
Transmission of SARS-CoV-2 by aerosols has played a significant role in the rapid spread of COVID19 across the globe
Able to capture the geometry of any room, along with any perturbing factors that will influence illumination and air flow, it does not suffer from the same constraints as practical measurements and allows more detailed analysis to be conducted, e.g. to ensure that far-UVC lamps are positioned optimally
One element of this study addresses the need for methods validation by applying the WYVERN high-fidelity coupled radiation-CFD code to reproduce the experimental measurements of 222 nm UVC inactivation of aerosolized coronavirus made at Columbia University[29]
Summary
Transmission of SARS-CoV-2 by aerosols has played a significant role in the rapid spread of COVID19 across the globe. In-room, 222 nm filtered far-UVC illumination has been suggested as a potential alternative approach, wherein aerosolized viruses are inactivated whilst transported in air flows within a r oom[27] The efficacy of this approach was predicted for a hospital room via use of the WYVERN highfidelity coupled radiation-CFD c ode[28]. Control over the fluence rate in the chamber was facilitated through placement of 222 nm far-UVC absorbing polymer films, held in place by the support rods, in front of the chamber window These filters transmitted 50% and 25% of the incident far-UVC light, respectively, allowing further measurements to be made at estimated doses of 1 and 0.5 mJ.cm−2. It does this by presenting the first highly-detailed model of the spatially varying flow fields and far-UVC fluence rates within the chamber, and provides the first fully-validated computational model of the far-UVC inactivation of aerosolized
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