Application of Portable Air Purifiers for Mitigating COVID-19 in Large Public Spaces
Round 1
Reviewer 1 Report
This article is about the usage of air purifiers to prevent the threat of COVID-19 infection. The results of the CFD analysis and the experiment were presented for two different rooms under different conditions. The article is clearly written and understandable and concerns a socially important topic.
Some remarks:
- Literature should be expanded, especially on the introduction.
- Equation 2 - please explain μ symbol in equation.
- Equation 4 - please explain meaning of the symbol on the left side of equation (F vector).
- Line 110 - 1.8 cm2 - index needed.
- Table 1 - "Distance between centers of manikin 1" - there are two values 1.1 and 1.3 m (lines 4 and 5). Which one is correct? Also, there is information about ceiling height in table 1.What about width and length of the ceiling?
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Table 2 - no information on the velocity of the air flowing out of the mouth. Was the velocity field homogeneous?
- Chapter 3 - How long was the simulation time for CFD calculations and during the experiment?
- Lines 288-290 - "The optimal location of the air purifier will be in proximity where people are seated, congregate or queue".
Has this information been confirmed by the CFD simulation results?
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
The study investigated the possibility portable air purifiers to reduce the infection risks of airborne respiratory diseases such as COVID-19. The study used two methods for reaching its scientific aim: experimental field studies in large public spaces such as a restaurant and a ballroom, together with CFD simulation.
The originality of the paper is high and the scientific content is of primary interest to science and society. The performed simulations are very well described and the results are credible. The same is valid for the field studies with thermal manikins.
The results obtained are important and show that portable air purifiers with HEPA filtration could be an effective solution to help mitigate virus-carrying particles in large spaces.
Some errors: clothe (row117), missing index of cm2 (row 110)
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Portable air filter has been recognized being able to reduce bio-aerosols concentration in door. This manuscript make a timely contribution presenting scientific research results of the portable air filters. I suggest that air flow field in the vicinity of the air filters be presented for further insight. Central air circulation tends to cause air mixing in a room, would it affect the flow field of the filter? The merit of a filter is not only one through filtering efficiency. Please also comment about the time taken in the experimental observation.
Author Response
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Author Response File: Author Response.pdf
Reviewer 4 Report
The article presents in a very rigorous and didactic way using validated computational fluid dynamics techniques, the actual performance of portable air purifiers in reducing the risks of infection of airborne respiratory diseases such as COVID-19. The authors must answer some questions before the article can be published.
1. How do the authors ensure adequate installation of air purifiers in large and complicated public spaces such as restaurants and dance halls of primary interest? L
2. With what percentage error or confidence level do the research results reveal that portable air purifiers with HEPA filtration provide an effective solution to help mitigate virus-carrying particles/droplets in large spaces where the central air conditioning system with HEPA filtration may not provide adequate dilution and/or effective ventilation.
3. Because it can be ensured that the deployment of a portable air purifier changes local flow directions and therefore reduces cross-flows of air increasing the possibility of cross-infection.
4. Because the field experiment was conducted in a restaurant and in a ballroom to verify on-site performance.
5. To enrich the state of the art, as it has little impact scientific referencing.
6. To make a discussion section based on results obtained by other researchers, of which the following articles should be included, which can also enrich the state of the art and should be referenced.
Ham, S. (2020). Prevention of exposure to and spread of COVID-19 using air purifiers: challenges and concerns. Epidemiology and Health. Korean Society of Epidemiology. https://0-doi-org.brum.beds.ac.uk/10.4178/epih.e2020027
Christopherson, D. A., Yao, W. C., Lu, M., Vijayakumar, R., & Sedaghat, A. R. (2020, December 1). High-Efficiency Particulate Air Filters in the Era of COVID-19: Function and Efficacy. Otolaryngology - Head and Neck Surgery (United States). SAGE Publications Inc. https://0-doi-org.brum.beds.ac.uk/10.1177/0194599820941838
Domínguez-amarillo, S., Fernández-agüera, J., Cesteros-garcía, S., & González-lezcano, R. A. (2020). Bad air can also kill: Residential indoor air quality and pollutant exposure risk during the covid-19 crisis. International Journal of Environmental Research and Public Health, 17(19), 1-34. https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph17197183
Mousavi, E. S., Godri Pollitt, K. J., Sherman, J., & Martinello, R. A. (2020). Performance analysis of portable HEPA filters and temporary plastic anterooms on the spread of surrogate coronavirus. Building and Environment, 183. https://0-doi-org.brum.beds.ac.uk/10.1016/j.buildenv.2020.107186
Fabisiak, B., Jankowska, A., & Kłos, R. (2020). Attitudes of Polish seniors toward the use of public space during the first wave of the COVID-19 pandemic. International Journal of Environmental Research and Public Health, 17(23), 1-17. https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph17238885
Hormigos-Jimenez, S., Padilla-Marcos, M. A., Meiss, A., Gonzalez-Lezcano, R. A., & Feijó-MuÑoz, J. (2018). Experimental validation of the age-of-the-air CFD analysis: A case study. Science and Technology for the Built Environment, 24(9), 994-1003. https://0-doi-org.brum.beds.ac.uk/10.1080/23744731.2018.1444885.
Honey-Rosés, J., Anguelovski, I., Chireh, V. K., Daher, C., Konijnendijk van den Bosch, C., Litt, J. S., ... Nieuwenhuijsen, M. J. (2020). The impact of COVID-19 on public space: an early review of the emerging questions - design, perceptions and inequities. Cities & Health, 1-17. https://0-doi-org.brum.beds.ac.uk/10.1080/23748834.2020.1780074
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 4 Report
The authors have made all suggested changes and corrections. The mind.article has been greatly improved
