Quantitative Microbial Risk Assessment for Airborne Transmission of Sars-Cov-2 and the Efficacy of Ultraviolet Germicidal Irradiation (UVGI) Systems
Abstract
The COVID-19 pandemic has raised awareness of the importance of controlling airborne disease agents. The ventilation system build in the indoor environments would facilitate the transmission of the airborne infectious diseases. And among engineering strategies, UV irradiation appears to present important advantages, relative to alternative strategies. However, whether the existing ventilation system can supply sufficient clean outdoor air for diluting the virus concentration remains unknow. To assess the performance of both treatment on reducing the infection risk, this study developed the Indoor Air Quality (IAQ) model that simulates the dynamics of airborne infective SARS-CoV-2 in a 500 m3 with or without mechanical ventilation and UV system. Then this model was linked to a quantitative microbial risk assessment (QMRA) to allow for estimation of the risk of disease transmission for a given treatment condition. The result showed that: 1) Considering its energy cost of heating, cooling, humidification, and dehumidification associated with an improvement of the system, and its little impact on the reduction of risk of infection, it was not a cost-effective method. 2) Mechanical ventilation alone was not likely to represent an effective measure for control of SARS-CoV-2 transmission, especially in situations where infected or noninfected individuals do not wear masks . 3) UV222 and UV254 had a better performance in reducing the risk of infection than a 15 hr-1 mechanical ventilation. Among them, Far-UVC system(UV222) has a similar potential with UV254 in terms of reduce the risk of transmission of airborne pathogens. When UV treatment was already applied, the effect of adding additional mechanical ventilation treatment was not obvious. 4) UVC system had good performance in reducing the risk of infection when infected individual in the room was likely to perform light activities that caused small viral emission rate (roughly <400 FFU>/hr). However, in places where people are more likely to emit big amount of virus (ie. Medical and healthcare facilities), engineering strategies such as UVC system was not sufficient in reducing the risk of infection, and it is critical to follow protocols that help reduce the viral emission, such as wearing face masks.
Degree
M.Sc.
Advisors
Blatchley, Purdue University.
Subject Area
Atmospheric sciences|Virology
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