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Park S, Won Y, Rim D. Formation and Transport of Secondary Contaminants Associated with Germicidal Ultraviolet Light Systems in an Occupied Classroom. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:12051-12061. [PMID: 38922431 DOI: 10.1021/acs.est.4c00575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/27/2024]
Abstract
Germicidal ultraviolet light (GUV) systems are designed to control airborne pathogen transmission in buildings. However, it is important to acknowledge that certain conditions and system configurations may lead GUV systems to produce air contaminants including oxidants and secondary organic aerosols (SOA). In this study, we modeled the formation and dispersion of oxidants and secondary contaminants generated by the operation of GUV systems employing ultraviolet C 254 and 222 nm. Using a three-dimensional computational fluid dynamics model, we examined the breathing zone concentrations of chemical species in an occupied classroom. Our findings indicate that operating GUV 222 leads to an approximate increase of 10 ppb in O3 concentration and 5.2 μg·m-3 in SOA concentration compared to a condition without GUV operation, while GUV 254 increases the SOA concentration by about 1.2 μg·m-3, with a minimal impact on the O3 concentration. Furthermore, increasing the UV fluence rate of GUV 222 from 1 to 5 μW·cm-2 results in up to 80% increase in the oxidants and SOA concentrations. For GUV 254, elevating the UV fluence rate from 30 to 50 μW·cm-2 or doubling the radiating volume results in up to 50% increase in the SOA concentration. Note that indoor airflow patterns, particularly buoyancy-driven airflow (or displacement ventilation), lead to 15-45% lower SOA concentrations in the breathing zone compared to well-mixed airflow. The results also reveal that when the ventilation rate is below 2 h-1, operating GUV 254 has a smaller impact on human exposure to secondary contaminants than GUV 222. However, GUV 254 may generate more contaminants than GUV 222 when operating at high indoor O3 levels (>15 ppb). These results suggest that the design of GUV systems should consider indoor O3 levels and room ventilation conditions.
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Affiliation(s)
- Seongjun Park
- Department of Architectural Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Youngbo Won
- Department of Architectural Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | - Donghyun Rim
- Department of Architectural Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, United States
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Pei G, Azimi P, Rim D, Allen JG. A CFD study on the effect of portable air cleaner placement on airborne infection control in a classroom. ENVIRONMENTAL SCIENCE. PROCESSES & IMPACTS 2024. [PMID: 38973672 DOI: 10.1039/d4em00114a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/09/2024]
Abstract
The utilization of portable air cleaners (PACs) is a recommended supplemental approach to help remove airborne pathogens and mitigate disease transmission in learning environments. To improve PAC effectiveness, science-based information is needed to optimize their implementation strategies such as the deployment location, height, and number of PACs. In this study, we developed a Computational Fluid Dynamics (CFD) model to assess how PACs perform in occupied classrooms equipped with displacement and mixing ventilation systems. The results show that PACs with a flow rate of 2.6 h-1 reduce the mean aerosol intake of all students by up to 66%. A key benefit of using PACs is to facilitate air mixing and movement in indoor environments with inadequate ventilation, thereby effectively reducing high aerosol concentrations near the infector. Furthermore, our results highlight the impact of PAC location on its performance. PACs achieve the best effectiveness when placed closed to the infector (within a distance <3 m). In the absence of knowing who is infected, deploying a PAC at the center of the room is recommended. Moreover, adjusting PAC flow discharge height to the breathing height of occupants (e.g., 0.9-1.2 m for seated people) can enhance their effectiveness in spaces with poor air mixing.
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Affiliation(s)
- Gen Pei
- Environmental Health Department, Harvard T. H. Chan School of Public Health, Boston, MA 02115, USA.
| | - Parham Azimi
- Environmental Health Department, Harvard T. H. Chan School of Public Health, Boston, MA 02115, USA.
| | - Donghyun Rim
- Architectural Engineering Department, Pennsylvania State University, University Park, PA 16802, USA
| | - Joseph G Allen
- Environmental Health Department, Harvard T. H. Chan School of Public Health, Boston, MA 02115, USA.
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Alqarni Z, Rezgui Y, Petri I, Ghoroghi A. Viral infection transmission and indoor air quality: A systematic review. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 923:171308. [PMID: 38432379 DOI: 10.1016/j.scitotenv.2024.171308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Revised: 02/03/2024] [Accepted: 02/25/2024] [Indexed: 03/05/2024]
Abstract
Respiratory disease transmission in indoor environments presents persistent challenges for health authorities, as exemplified by the recent COVID-19 pandemic. This underscores the urgent necessity to investigate the dynamics of viral infection transmission within indoor environments. This systematic review delves into the methodologies of respiratory infection transmission in indoor settings and explores how the quality of indoor air (IAQ) can be controlled to alleviate this risk while considering the imperative of sustainability. Among the 2722 articles reviewed, 178 were retained based on their focus on respiratory viral infection transmission and IAQ. Fifty eight articles delved into SARS-CoV-2 transmission, 21 papers evaluated IAQ in contexts of other pandemics, 53 papers assessed IAQ during the SARS-CoV-2 pandemic, and 46 papers examined control strategies to mitigate infectious transmission. Furthermore, of the 46 papers investigating control strategies, only nine considered energy consumption. These findings highlight clear gaps in current research, such as analyzing indoor air and surface samples for specific indoor environments, oversight of indoor and outdoor parameters (e.g., temperature, relative humidity (RH), and building orientation), neglect of occupancy schedules, and the absence of considerations for energy consumption while enhancing IAQ. This study distinctly identifies the indoor environmental conditions conducive to the thriving of each respiratory virus, offering IAQ trade-offs to mitigate the risk of dominant viruses at any given time. This study argues that future research should involve digital twins in conjunction with machine learning (ML) techniques. This approach aims to enhance IAQ by analyzing the transmission patterns of various respiratory viruses while considering energy consumption.
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Affiliation(s)
- Zahi Alqarni
- School of Engineering, Cardiff University, Cardiff CF24 3AA, UK; School of Computer Science, King Khalid University, Abha 62529, Saudi Arabia.
| | - Yacine Rezgui
- School of Engineering, Cardiff University, Cardiff CF24 3AA, UK
| | - Ioan Petri
- School of Engineering, Cardiff University, Cardiff CF24 3AA, UK
| | - Ali Ghoroghi
- School of Engineering, Cardiff University, Cardiff CF24 3AA, UK
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Obeid S, White P, Rosati Rowe J, Ilacqua V, Rawat MS, Ferro AR, Ahmadi G. Airborne respiratory aerosol transport and deposition in a two-person office using a novel diffusion-based numerical model. JOURNAL OF EXPOSURE SCIENCE & ENVIRONMENTAL EPIDEMIOLOGY 2024; 34:356-375. [PMID: 37337048 DOI: 10.1038/s41370-023-00546-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Revised: 03/24/2023] [Accepted: 03/30/2023] [Indexed: 06/21/2023]
Abstract
BACKGROUND The COVID-19 pandemic was caused by the SARS-CoV-2 coronaviruses transmitted mainly through exposure to airborne respiratory droplets and aerosols carrying the virus. OBJECTIVE To assess the transport and dispersion of respiratory aerosols containing the SARS-CoV-2 virus and other viruses in a small office space using a diffusion-based computational modeling approach. METHODS A 3-D computational model was used to simulate the airflow inside the 70.2 m3 ventilated office. A novel diffusion model accounting for turbulence dispersion and gravitational sedimentation was utilized to predict droplet concentration transport and deposition. The numerical model was validated and used to investigate the influences of partition height and different ventilation rates on the concentration of respiratory aerosols of various sizes (1, 10, 20, and 50 µm) emitted by continuous speaking. RESULTS An increase in the hourly air change rate (ACH) from 2.0 to 5.6 decreased the 1 μm droplet concentration inside the office by a factor of 2.8 and in the breathing zone of the receptor occupant by a factor of 3.2. The concentration at the receptor breathing zone is estimated by the area-weighted average of a 1 m diameter circular disk, with its centroid at the center of the receptor mannequin mouth. While all aerosols were dispersed by airflow turbulence, the gravitational sedimentation significantly influenced the transport of larger aerosols in the room. The 1 and 10 μm aerosols remained suspended in the air and dispersed throughout the room. In contrast, the larger 20 and 50 μm aerosols deposited on the floor quickly due to the gravitational sedimentation. Increasing the partition between cubicles by 0.254 m (10") has little effect on the smaller aerosols and overall exposure. IMPACT This paper provides an efficient computational model for analyzing the concentration of different respiratory droplets and aerosols in an indoor environment. Thus, the approach could be used for assessing the influence of the spatial concentration variations on exposure for which the fully mixed model cannot be used.
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Affiliation(s)
- Sohaib Obeid
- Department of Mechanical and Aerospace Engineering, Clarkson University, Potsdam, NY, 13699, USA
| | - Paul White
- U.S. Environmental Protection Agency (EPA), Office of Research and Development, Research Triangle Park, Washington, DC, NC, USA
| | - Jacky Rosati Rowe
- U.S. Environmental Protection Agency (EPA), Office of Research and Development, Research Triangle Park, Washington, DC, NC, USA
| | - Vito Ilacqua
- U.S. Environmental Protection Agency (EPA), Office of Research and Development, Research Triangle Park, Washington, DC, NC, USA
| | - Mahender Singh Rawat
- Department of Civil and Environmental Engineering, Clarkson University, Potsdam, NY, 13699, USA
| | - Andrea R Ferro
- Department of Mechanical and Aerospace Engineering, Clarkson University, Potsdam, NY, 13699, USA
| | - Goodarz Ahmadi
- Department of Mechanical and Aerospace Engineering, Clarkson University, Potsdam, NY, 13699, USA.
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Mokryn O, Abbey A, Marmor Y, Shahar Y. Evaluating the dynamic interplay of social distancing policies regarding airborne pathogens through a temporal interaction-driven model that uses real-world and synthetic data. J Biomed Inform 2024; 151:104601. [PMID: 38307358 DOI: 10.1016/j.jbi.2024.104601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2023] [Revised: 12/18/2023] [Accepted: 01/27/2024] [Indexed: 02/04/2024]
Abstract
OBJECTIVE The recent SARS-CoV-2 pandemic has exhibited diverse patterns of spread across countries and communities, emphasizing the need to consider the underlying population dynamics in modeling its progression and the importance of evaluating the effectiveness of non-pharmaceutical intervention strategies in combating viral transmission within human communities. Such an understanding requires accurate modeling of the interplay between the community dynamics and the disease propagation dynamics within the community. METHODS We build on an interaction-driven model of an airborne disease over contact networks that we have defined. Using the model, we evaluate the effectiveness of temporal, spatial, and spatiotemporal social distancing policies. Temporal social distancing involves a pure dilation of the timeline while preserving individual activity potential and thus prolonging the period of interaction; spatial distancing corresponds to social distancing pods; and spatiotemporal distancing pertains to the situation in which fixed subgroups of the overall group meet at alternate times. We evaluate these social distancing policies over real-world interactions' data and over history-preserving synthetic temporal random networks. Furthermore, we evaluate the policies for the disease's with different number of initial patients, corresponding to either the phase in the progression of the infection through a community or the number of patients infected together at the initial infection event. We expand our model to consider the exposure to viral load, which we correlate with the meetings' duration. RESULTS Our results demonstrate the superiority of decreasing social interactions (i.e., time dilation) within the community over partial isolation strategies, such as the spatial distancing pods and the spatiotemporal distancing strategy. In addition, we found that slow-spreading pathogens (i.e., pathogens that require a longer exposure to infect) spread roughly at the same rate as fast-spreading ones in highly active communities. This result is surprising since the pathogens may follow different paths. However, we demonstrate that the dilation of the timeline considerably slows the spread of the slower pathogens. CONCLUSIONS Our results demonstrate that the temporal dynamics of a community have a more significant effect on the spread of the disease than the characteristics of the spreading processes.
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Affiliation(s)
- Osnat Mokryn
- Department of Information Systems, University of Haifa, Israel.
| | - Alex Abbey
- Department of Information Systems, University of Haifa, Israel
| | - Yanir Marmor
- Department of Information Systems, University of Haifa, Israel
| | - Yuval Shahar
- Department of Software and Information Systems Engineering, Ben Gurion University, Beer-Sheva, Israel
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Park S, Mistrick R, Sitzabee W, Rim D. Effect of ventilation strategy on performance of upper-room ultraviolet germicidal irradiation (UVGI) system in a learning environment. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 899:165454. [PMID: 37467991 DOI: 10.1016/j.scitotenv.2023.165454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2022] [Revised: 06/22/2023] [Accepted: 07/08/2023] [Indexed: 07/21/2023]
Abstract
Upper-room ultraviolet germicidal irradiation (UVGI) system is recently in the limelight as a potentially effective method to mitigate the risk of airborne virus infection in indoor environments. However, few studies quantitatively evaluated the relationship between ventilation effectiveness and virus disinfection performance of a UVGI system. The objective of this study is to investigate the effects of ventilation strategy on detailed airflow distributions and UVGI disinfection performance in an occupied classroom. Three-dimensional computational fluid dynamics (CFD) simulations were performed for representative cooling, heating, and ventilation scenarios. The results show that when the ventilation rate is 1.1 h-1 (the minimum ventilation rate based on ASHRAE 62.1), enhancing indoor air circulation with the mixing fan notably improves the UVGI disinfection performance, especially for cooling with displacement ventilation and all-air-heating conditions. However, increasing indoor air mixing yields negligible effect on the disinfection performance for forced-convection cooling condition. The results also reveal that regardless of indoor thermal condition, disinfection effectiveness of a UVGI system increases as ventilation effectiveness is close to unity. Moreover, when the room average air speed is >0.1 m/s, upper-room UVGI system could yield about 90% disinfection effect for the aerosol size of 1 μm-10 μm. The findings of this study imply that upper-room UVGI systems in indoor environments (i.e., classrooms, hospitals) should be designed considering ventilation strategy and occupancy conditions, especially for occupied buildings with insufficient air mixing throughout the space.
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Affiliation(s)
- Seongjun Park
- Department of Architectural Engineering, Pennsylvania State University, United States of America.
| | - Richard Mistrick
- Architectural Engineering Department, Pennsylvania State University, 104 Engineering Unit A, University Park, PA 16802, United States of America.
| | - William Sitzabee
- Pennsylvania State University, 201 Physical Plant Building, University Park, PA 16802, United States of America.
| | - Donghyun Rim
- Architectural Engineering Department, Pennsylvania State University, 222 Engineering Unit A, University Park, PA 16802, United States of America.
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Marmor Y, Abbey A, Shahar Y, Mokryn O. Assessing individual risk and the latent transmission of COVID-19 in a population with an interaction-driven temporal model. Sci Rep 2023; 13:12955. [PMID: 37563358 PMCID: PMC10415258 DOI: 10.1038/s41598-023-39817-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Accepted: 07/31/2023] [Indexed: 08/12/2023] Open
Abstract
Interaction-driven modeling of diseases over real-world contact data has been shown to promote the understanding of the spread of diseases in communities. This temporal modeling follows the path-preserving order and timing of the contacts, which are essential for accurate modeling. Yet, other important aspects were overlooked. Various airborne pathogens differ in the duration of exposure needed for infection. Also, from the individual perspective, Covid-19 progression differs between individuals, and its severity is statistically correlated with age. Here, we enrich an interaction-driven model of Covid-19 and similar airborne viral diseases with (a) meetings duration and (b) personal disease progression. The enriched model enables predicting outcomes at both the population and the individual levels. It further allows predicting individual risk of engaging in social interactions as a function of the virus characteristics and its prevalence in the population. We further showed that the enigmatic nature of asymptomatic transmission stems from the latent effect of the network density on this transmission and that asymptomatic transmission has a substantial impact only in sparse communities.
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Affiliation(s)
- Yanir Marmor
- Information Systems, University of Haifa, Haifa, Israel
| | - Alex Abbey
- Information Systems, University of Haifa, Haifa, Israel
| | - Yuval Shahar
- Software and Information Systems Engineering, Ben Gurion University, Beer Sheva, Israel
| | - Osnat Mokryn
- Information Systems, University of Haifa, Haifa, Israel.
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Ren C, Zhu HC, Wang J, Feng Z, Chen G, Haghighat F, Cao SJ. Intelligent operation, maintenance, and control system for public building: Towards infection risk mitigation and energy efficiency. SUSTAINABLE CITIES AND SOCIETY 2023; 93:104533. [PMID: 36941886 PMCID: PMC10017170 DOI: 10.1016/j.scs.2023.104533] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Revised: 02/07/2023] [Accepted: 03/14/2023] [Indexed: 06/18/2023]
Abstract
During the post-COVID-19 era, it is important but challenging to synchronously mitigate the infection risk and optimize the energy savings in public buildings. While, ineffective control of ventilation and purification systems can result in increased energy consumption and cross-contamination. This paper is to develop intelligent operation, maintenance, and control systems by coupling intelligent ventilation and air purification systems (negative ion generators). Optimal deployment of sensors is determined by Fuzzy C-mean (FCM), based on which CO2 concentration fields are rapidly predicted by combing the artificial neural network (ANN) and self-adaptive low-dimensional linear model (LLM). Negative oxygen ion and particle concentrations are simulated with different numbers of negative ion generators. Optimal ventilation rates and number of negative ion generators are decided. A visualization platform is established to display the effects of ventilation control, epidemic prevention, and pollutant removal. The rapid prediction error of LLM-based ANN for CO2 concentration was below 10% compared with the simulation. Fast decision reduced CO2 concentration below 1000 ppm, infection risk below 1.5%, and energy consumption by 27.4%. The largest removal efficiency was 81% when number of negative ion generators was 10. This work can promote intelligent operation, maintenance, and control systems considering infection prevention and energy sustainability.
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Affiliation(s)
- Chen Ren
- School of Architecture, Southeast University, Nanjing, 210096, China
| | - Hao-Cheng Zhu
- School of Architecture, Southeast University, Nanjing, 210096, China
| | - Junqi Wang
- School of Architecture, Southeast University, Nanjing, 210096, China
- School of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou, 215009, China
| | - Zhuangbo Feng
- School of Architecture, Southeast University, Nanjing, 210096, China
| | - Gang Chen
- The Third Construction Co., Ltd of China Construction Eighth Engineering Division, Nanjing, 210046, China
| | - Fariborz Haghighat
- Energy and Environment Group, Department of Building, Civil and Environmental Engineering, Concordia University, Montreal, H3G 1M8, Canada
| | - Shi-Jie Cao
- School of Architecture, Southeast University, Nanjing, 210096, China
- Global Centre for Clean Air Research, Department of Civil and Environmental Engineering, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, GU2 7XH, United Kingdom
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Moschovis PP, Lombay J, Rooney J, Schenkel SR, Singh D, Rezaei SJ, Salo N, Gong A, Yonker LM, Shah J, Hayden D, Hibberd PL, Demokritou P, Kinane TB. The effect of activity and face masks on exhaled particles in children. Pediatr Investig 2023; 7:75-85. [PMID: 37324601 PMCID: PMC10262878 DOI: 10.1002/ped4.12376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2022] [Accepted: 01/29/2023] [Indexed: 06/17/2023] Open
Abstract
Importance Despite the high burden of respiratory infections among children, the production of exhaled particles during common activities and the efficacy of face masks in children have not been sufficiently studied. Objective To determine the effect of type of activity and mask usage on exhaled particle production in children. Methods Healthy children were asked to perform activities that ranged in intensity (breathing quietly, speaking, singing, coughing, and sneezing) while wearing no mask, a cloth mask, or a surgical mask. The concentration and size of exhaled particles were assessed during each activity. Results Twenty-three children were enrolled in the study. Average exhaled particle concentration increased by intensity of activity, with the lowest particle concentration during tidal breathing (1.285 particles/cm3 [95% CI 0.943, 1.627]) and highest particle concentration during sneezing (5.183 particles/cm3 [95% CI 1.911, 8.455]). High-intensity activities were associated with an increase primarily in the respirable size (≤ 5 µm) particle fraction. Surgical and cloth masks were associated with lower average particle concentration compared to no mask (P = 0.026 for sneezing). Surgical masks outperformed cloth masks across all activities, especially within the respirable size fraction. In a multivariable linear regression model, we observed significant effect modification of activity by age and by mask type. Interpretation Similar to adults, children produce exhaled particles that vary in size and concentration across a range of activities. Production of respirable size fraction particles (≤ 5 µm), the dominant mode of transmission of many respiratory viruses, increases significantly with coughing and sneezing and is most effectively reduced by wearing surgical face masks.
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Affiliation(s)
- Peter P. Moschovis
- Department of PediatricsMassachusetts General Hospital and Harvard Medical SchoolBostonMassachusettsUSA
| | - Jesiel Lombay
- Department of PediatricsMassachusetts General Hospital and Harvard Medical SchoolBostonMassachusettsUSA
| | - Jennifer Rooney
- Department of PediatricsMassachusetts General Hospital and Harvard Medical SchoolBostonMassachusettsUSA
| | - Sara R. Schenkel
- Department of PediatricsMassachusetts General Hospital and Harvard Medical SchoolBostonMassachusettsUSA
| | - Dilpreet Singh
- Department of Environmental HealthHarvard T. H. Chan School of Public HealthBostonMassachusettsUSA
- Department of Mechanical and Aerospace EngineeringRutgers University School of Public HealthNew BrunswickNew JerseyUSA
| | - Shawheen J. Rezaei
- Department of PediatricsMassachusetts General Hospital and Harvard Medical SchoolBostonMassachusettsUSA
| | - Nora Salo
- Department of PediatricsMassachusetts General Hospital and Harvard Medical SchoolBostonMassachusettsUSA
| | - Amanda Gong
- David Geffen School of Medicinethe University of California Los AngelesLos AngelesCaliforniaUSA
| | - Lael M. Yonker
- Department of PediatricsMassachusetts General Hospital and Harvard Medical SchoolBostonMassachusettsUSA
| | - Jhill Shah
- Department of PediatricsMassachusetts General Hospital and Harvard Medical SchoolBostonMassachusettsUSA
| | - Douglas Hayden
- Department of PediatricsMassachusetts General Hospital and Harvard Medical SchoolBostonMassachusettsUSA
| | - Patricia L. Hibberd
- Department of Global HealthBoston University School of Public HealthBostonMassachusettsUSA
| | - Philip Demokritou
- Department of Environmental HealthHarvard T. H. Chan School of Public HealthBostonMassachusettsUSA
- Department of Mechanical and Aerospace EngineeringRutgers University School of Public HealthNew BrunswickNew JerseyUSA
| | - T. Bernard Kinane
- Department of PediatricsMassachusetts General Hospital and Harvard Medical SchoolBostonMassachusettsUSA
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Liu F, Luo Z, Qian H. Impact of thermal stratification on airborne transmission risk of SARS-CoV-2 in various indoor environments. BUILDING SIMULATION 2023; 16:1-14. [PMID: 37359828 PMCID: PMC10166632 DOI: 10.1007/s12273-023-1021-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2022] [Revised: 03/08/2023] [Accepted: 03/22/2023] [Indexed: 06/28/2023]
Abstract
There exist various vertical temperature gradients in different-type buildings. A holistic understanding of the impact of different temperature-stratified indoor environments on infection risk is necessary. In this work, the airborne transmission risk of SARS-CoV-2 in different thermally stratified indoor environments is assessed using our previously developed airborne infection risk model. Results show that the vertical temperature gradients in office building, hospital, classroom, etc. are within the range of -0.34 to 3.26 °C/m. In large space such as coach station, airport terminal, and sport hall, the average temperature gradient ranges within 0.13-2.38 °C/m in occupied zone (0-3 m); in ice rink with special requirements of indoor environment, the temperature gradient is higher than those in the above indoor spaces. The existence of temperature gradients causes multi-peaks of the transmission risk of SARS-CoV-2 with distancing, and our results show that in office, hospital ward and classroom, the second peak of the transmission risk is higher than 10-3 in most contact scenarios, while most being lower than 10-6 in large spaces like coach station and airport. The work is expected to provide some guidance on specific intervention policies in relation to the types of indoor environments. Electronic Supplementary Material the Appendix is available in the online version of this article at 10.1007/s12273-023-1021-5.
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Affiliation(s)
- Fan Liu
- School of Environment and Architecture, University of Shanghai for Science and Technology, Shanghai, China
| | - Zhiwen Luo
- Welsh School of Architecture, Cardiff University, Cardiff, UK
| | - Hua Qian
- School of Energy and Environment, Southeast University, Nanjing, China
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11
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A review on indoor airborne transmission of COVID-19– modelling and mitigation approaches. JOURNAL OF BUILDING ENGINEERING 2023; 64:105599. [PMCID: PMC9699823 DOI: 10.1016/j.jobe.2022.105599] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 11/11/2022] [Accepted: 11/21/2022] [Indexed: 06/09/2023]
Abstract
In the past few years, significant efforts have been made to investigate the transmission of COVID-19. This paper provides a review of the COVID-19 airborne transmission modeling and mitigation strategies. The simulation models here are classified into airborne transmission infectious risk models and numerical approaches for spatiotemporal airborne transmissions. Mathematical descriptions and assumptions on which these models have been based are discussed. Input data used in previous simulation studies to assess the dispersion of COVID-19 are extracted and reported. Moreover, measurements performed to study the COVID-19 airborne transmission within indoor environments are introduced to support validations for anticipated future modeling studies. Transmission mitigation strategies recommended in recent studies have been classified to include modifying occupancy and ventilation operations, using filters and air purifiers, installing ultraviolet (UV) air disinfection systems, and personal protection compliance, such as wearing masks and social distancing. The application of mitigation strategies to various building types, such as educational, office, public, residential, and hospital, is reviewed. Recommendations for future works are also discussed based on the current apparent knowledge gaps covering both modeling and mitigation approaches. Our findings show that different transmission mitigation measures were recommended for various indoor environments; however, there is no conclusive work reporting their combined effects on the level of mitigation that may be achieved. Moreover, further studies should be conducted to understand better the balance between approaches to mitigating the viral transmissions in buildings and building energy consumption.
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12
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Glenn K, He J, Rochlin R, Teng S, Hecker JG, Novosselov I. Assessment of aerosol persistence in ICUs via low-cost sensor network and zonal models. Sci Rep 2023; 13:3992. [PMID: 36899063 PMCID: PMC10006437 DOI: 10.1038/s41598-023-30778-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2022] [Accepted: 03/01/2023] [Indexed: 03/12/2023] Open
Abstract
The COVID-19 pandemic raised public awareness about airborne particulate matter (PM) due to the spread of infectious diseases via the respiratory route. The persistence of potentially infectious aerosols in public spaces and the spread of nosocomial infections in medical settings deserve careful investigation; however, a systematic approach characterizing the fate of aerosols in clinical environments has not been reported. This paper presents a methodology for mapping aerosol propagation using a low-cost PM sensor network in ICU and adjacent environments and the subsequent development of the data-driven zonal model. Mimicking aerosol generation by a patient, we generated trace NaCl aerosols and monitored their propagation in the environment. In positive (closed door) and neutral-pressure (open door) ICUs, up to 6% or 19%, respectively, of all PM escaped through the door gaps; however, the outside sensors did not register an aerosol spike in negative-pressure ICUs. The K-means clustering analysis of temporospatial aerosol concentration data suggests that ICU can be represented by three distinct zones: (1) near the aerosol source, (2) room periphery, and (3) outside the room. The data suggests two-phase plume behavior: dispersion of the original aerosol spike throughout the room, followed by an evacuation phase where "well-mixed" aerosol concentration decayed uniformly. Decay rates were calculated for positive, neutral, and negative pressure operations, with negative-pressure rooms clearing out nearly twice as fast. These decay trends closely followed the air exchange rates. This research demonstrates the methodology for aerosol monitoring in medical settings. This study is limited by a relatively small data set and is specific to single-occupancy ICU rooms. Future work needs to evaluate medical settings with high risks of infectious disease transmission.
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Affiliation(s)
- K Glenn
- Department of Mechanical Engineering, University of Washington, Seattle, USA
| | - J He
- Department of Mechanical Engineering, University of Washington, Seattle, USA
| | - R Rochlin
- Department of Mechanical Engineering, University of Washington, Seattle, USA
| | - S Teng
- Department of Mechanical Engineering, University of Washington, Seattle, USA
| | - J G Hecker
- Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, USA
| | - I Novosselov
- Department of Mechanical Engineering, University of Washington, Seattle, USA.
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13
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Bahramian A. Influence of indoor environmental conditions on airborne transmission and lifetime of sneeze droplets in a confined space: a way to reduce COVID-19 spread. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2023; 30:44067-44085. [PMID: 36680724 PMCID: PMC9867553 DOI: 10.1007/s11356-023-25421-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Accepted: 01/16/2023] [Indexed: 06/17/2023]
Abstract
Effects of indoor temperature (T∞) and relative humidity (RH∞) on the airborne transmission of sneeze droplets in a confined space were studied over the T∞ range of 15-30 °C and RH∞ of 22-62%. In addition, a theoretical evaporation model was used to estimate the droplet lifetime based on experimental data. The results showed that the body mass index (BMI) of the participants played an important role in the sneezing jet velocity, while the impact of the BMI and gender of participants was insignificant on the size distribution of droplets. At a critical relative humidity RH∞,crit of 46%, the sneezing jet velocity and droplet lifetime were roughly independent of T∞. At RH∞ < RH∞,crit, the sneezing jet velocity decreased by increasing T∞ from 15 to 30 °C, while its trend was reversed at RH∞ > RH∞,crit. The maximum spreading distance of aerosols increased by decreasing the RH∞ and increasing T∞, while the droplet lifetime increased by decreasing T∞ at RH∞ > RH∞,crit. The mean diameter of aerosolized droplets was less affected by T∞ than the large droplets at RH∞ < RH∞,crit, while the mean diameter and number fraction of aerosols were more influenced by RH∞ than the T∞ in the range of 46% ≤ RH∞ ≤ 62%. In summary, this study suggests suitable indoor environmental conditions by considering the transmission rate and lifetime of respiratory droplets to reduce the spread of COVID-19.
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Affiliation(s)
- Alireza Bahramian
- Department of Chemical Engineering, Hamedan University of Technology, P.O. Box, Hamedan, 65155, Iran.
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14
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Chen W, Liu L, Zhang N, Hang J, Li Y. Conversational head movement decreases close-contact exposure to expired respiratory droplets. JOURNAL OF HAZARDOUS MATERIALS 2023; 444:130406. [PMID: 36417778 DOI: 10.1016/j.jhazmat.2022.130406] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 11/01/2022] [Accepted: 11/13/2022] [Indexed: 06/16/2023]
Abstract
People constantly move their heads during conversation, as such movement is an important non-verbal mode of communication. Head movement alters the direction of people's expired air flow, therefore affecting their conversational partners' level of exposure. Nevertheless, there is a lack of understanding of the mechanism whereby head movement affects people's exposure. In this study, a dynamic meshing method in computational fluid dynamics was used to simulate the head movement of a human-shaped thermal manikin. Droplets were released during the oral expiration periods of the source manikin, during which it was either motionless, was shaking its head or was nodding its head, while the head of a face-to-face target manikin remained motionless. The results indicate that the target manikin had a high level of exposure to respiratory droplets when the source manikin was motionless, whereas the target manikin's level of exposure was significantly reduced when the source manikin was shaking or nodding its head. The source manikin had the highest level of self-exposure when it was nodding its head and the lowest level of self-exposure when its head was motionless. People's level of exposure during close contact is highly variable, highlighting the need for further investigations in more realistic conversational scenarios.
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Affiliation(s)
- Wenzhao Chen
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China
| | - Li Liu
- Department of Building Science, Tsinghua University, Beijing 100084, China
| | - Nan Zhang
- Beijing Key Laboratory of Green Built Environment and Energy Efficient Technology, Beijing University of Technology, Beijing, China
| | - Jian Hang
- School of Atmospheric Sciences, Sun Yat-sen University, and Southern Marine Science and Engineering Guangdong Laboratory, Zhuhai 519082, China
| | - Yuguo Li
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China; Faculty of Architecture, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
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15
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Kapoor NR, Kumar A, Kumar A, Zebari DA, Kumar K, Mohammed MA, Al-Waisy AS, Albahar MA. Event-Specific Transmission Forecasting of SARS-CoV-2 in a Mixed-Mode Ventilated Office Room Using an ANN. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2022; 19:16862. [PMID: 36554744 PMCID: PMC9779012 DOI: 10.3390/ijerph192416862] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/05/2022] [Revised: 12/08/2022] [Accepted: 12/12/2022] [Indexed: 06/17/2023]
Abstract
The emerging novel variants and re-merging old variants of SARS-CoV-2 make it critical to study the transmission probability in mixed-mode ventilated office environments. Artificial neural network (ANN) and curve fitting (CF) models were created to forecast the R-Event. The R-Event is defined as the anticipated number of new infections that develop in particular events occurring over the course of time in any defined space. In the spring and summer of 2022, real-time data for an office environment were collected in India in a mixed-mode ventilated office space in a composite climate. The performances of the proposed CF and ANN models were compared with respect to traditional statistical indicators, such as the correlation coefficient, RMSE, MAE, MAPE, NS index, and a20-index, in order to determine the merit of the two approaches. Thirteen input features, namely the indoor temperature (TIn), indoor relative humidity (RHIn), area of opening (AO), number of occupants (O), area per person (AP), volume per person (VP), CO2 concentration (CO2), air quality index (AQI), outer wind speed (WS), outdoor temperature (TOut), outdoor humidity (RHOut), fan air speed (FS), and air conditioning (AC), were selected to forecast the R-Event as the target. The main objective was to determine the relationship between the CO2 level and R-Event, ultimately producing a model for forecasting infections in office building environments. The correlation coefficients for the CF and ANN models in this case study were 0.7439 and 0.9999, respectively. This demonstrates that the ANN model is more accurate in R-Event prediction than the curve fitting model. The results show that the proposed ANN model is reliable and significantly accurate in forecasting the R-Event values for mixed-mode ventilated offices.
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Affiliation(s)
- Nishant Raj Kapoor
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
- Architecture and Planning Department, CSIR-Central Building Research Institute, Roorkee 247667, India
| | - Ashok Kumar
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
- Architecture and Planning Department, CSIR-Central Building Research Institute, Roorkee 247667, India
| | - Anuj Kumar
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
- Building Energy Efficiency Division, CSIR-Central Building Research Institute, Roorkee 247667, India
| | - Dilovan Asaad Zebari
- Department of Computer Science, College of Science, Nawroz University, Duhok 42001, Iraq
| | - Krishna Kumar
- Department of Hydro and Renewable Energy, Indian Institute of Technology, Roorkee 247667, India
| | - Mazin Abed Mohammed
- College of Computer Science and Information Technology, University of Anbar, Anbar 31001, Iraq
| | - Alaa S. Al-Waisy
- Computer Technologies Engineering Department, Information Technology College, Imam Ja’afar Al-Sadiq University, Baghdad 10064, Iraq
| | - Marwan Ali Albahar
- School of Computer Science, Umm Al-Qura University, Mecca 24382, Saudi Arabia
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16
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Argyropoulos CD, Skoulou V, Efthimiou G, Michopoulos AK. Airborne transmission of biological agents within the indoor built environment: a multidisciplinary review. AIR QUALITY, ATMOSPHERE, & HEALTH 2022; 16:477-533. [PMID: 36467894 PMCID: PMC9703444 DOI: 10.1007/s11869-022-01286-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 11/17/2022] [Indexed: 06/17/2023]
Abstract
The nature and airborne dispersion of the underestimated biological agents, monitoring, analysis and transmission among the human occupants into building environment is a major challenge of today. Those agents play a crucial role in ensuring comfortable, healthy and risk-free conditions into indoor working and leaving spaces. It is known that ventilation systems influence strongly the transmission of indoor air pollutants, with scarce information although to have been reported for biological agents until 2019. The biological agents' source release and the trajectory of airborne transmission are both important in terms of optimising the design of the heating, ventilation and air conditioning systems of the future. In addition, modelling via computational fluid dynamics (CFD) will become a more valuable tool in foreseeing risks and tackle hazards when pollutants and biological agents released into closed spaces. Promising results on the prediction of their dispersion routes and concentration levels, as well as the selection of the appropriate ventilation strategy, provide crucial information on risk minimisation of the airborne transmission among humans. Under this context, the present multidisciplinary review considers four interrelated aspects of the dispersion of biological agents in closed spaces, (a) the nature and airborne transmission route of the examined agents, (b) the biological origin and health effects of the major microbial pathogens on the human respiratory system, (c) the role of heating, ventilation and air-conditioning systems in the airborne transmission and (d) the associated computer modelling approaches. This adopted methodology allows the discussion of the existing findings, on-going research, identification of the main research gaps and future directions from a multidisciplinary point of view which will be helpful for substantial innovations in the field.
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Affiliation(s)
| | - Vasiliki Skoulou
- B3 Challenge Group, Chemical Engineering, School of Engineering, University of Hull, Cottingham Road, Hull, HU6 7RX UK
| | - Georgios Efthimiou
- Centre for Biomedicine, Hull York Medical School, University of Hull, Cottingham Road, Hull, HU6 7RX UK
| | - Apostolos K. Michopoulos
- Energy & Environmental Design of Buildings Research Laboratory, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus
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17
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Cheung T, Li J, Goh J, Sekhar C, Cheong D, Tham KW. Evaluation of aerosol transmission risk during home quarantine under different operating scenarios: A pilot study. BUILDING AND ENVIRONMENT 2022; 225:109640. [PMID: 36210963 PMCID: PMC9528801 DOI: 10.1016/j.buildenv.2022.109640] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Revised: 09/22/2022] [Accepted: 09/24/2022] [Indexed: 06/09/2023]
Abstract
SARS-CoV-2 has been recognized to be airborne transmissible. With the large number of reported positive cases in the community, home quarantine is recommended for the infectors who are not severely ill. However, the risks of household aerosol transmission associated with the quarantine room operating methods are under-explored. We used tracer gas technique to simulate the exhaled virus laden aerosols from a patient under home quarantine situation inside a residential testbed. The Sulphur hexafluoride (SF6) concentration was measured both inside and outside the quarantine room under different operating settings including, air-conditioning and natural ventilation, presence of an exhaust fan, and the air movement generated by ceiling or pedestal fan. We calculated the outside-to-inside SF6 concentration to indicate potential exposure of occupants in the same household. In-room concentration with air-conditioning was 4 times higher than in natural ventilation settings. Exhaust fan operation substantially reduced in-room SF6 concentration and leakage rate in most of the ventilation scenarios, except for natural ventilation setting with ceiling fan. The exception is attributable to the different airflow patterns between ceiling fan (recirculates air vertically) and pedestal fan (moves air horizontally). These airflow variations also led to differences in SF6 concentration at two sampling heights (0.1 m and 1.7 m) and SF6 leakage rates when the quarantine room door was opened momentarily. Use of natural ventilation rather than air-conditioning, and operating exhaust fan when using air-conditioning are recommended to lower exposure risk for home quarantine. A more holistic experiment will be conducted to address the limitations reflected in this study.
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Affiliation(s)
- Toby Cheung
- Department of the Built Environment, National University of Singapore, Singapore
| | - Jiayu Li
- Berkeley Education Alliance for Research in Singapore (BEARS), Singapore
| | - Jiamin Goh
- Department of the Built Environment, National University of Singapore, Singapore
| | - Chandra Sekhar
- Department of the Built Environment, National University of Singapore, Singapore
| | - David Cheong
- Department of the Built Environment, National University of Singapore, Singapore
| | - Kwok Wai Tham
- Department of the Built Environment, National University of Singapore, Singapore
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18
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Adzic F, Roberts BM, Hathway EA, Kaur Matharu R, Ciric L, Wild O, Cook M, Malki-Epshtein L. A post-occupancy study of ventilation effectiveness from high-resolution CO 2 monitoring at live theatre events to mitigate airborne transmission of SARS-CoV-2. BUILDING AND ENVIRONMENT 2022; 223:109392. [PMID: 35937085 PMCID: PMC9339161 DOI: 10.1016/j.buildenv.2022.109392] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 06/24/2022] [Accepted: 07/10/2022] [Indexed: 05/20/2023]
Abstract
Mass-gathering events were closed around the world in 2020 to minimise the spread of the SARS-CoV-2 virus. Emerging research on the transmission of SARS-CoV-2 emphasised the importance of sufficient ventilation. This paper presents the results of an indoor air quality (IAQ) monitoring study over 82 events in seven mechanically ventilated auditoria to support the UK government Events Research Programme. Indoor carbon dioxide concentration was measured at high resolution before, during, and after occupancy to allow for assessment of the ventilation systems. Generally, good indoor air quality was measured in all auditoria, with average IAQ found to be excellent or very good for 70% of spaces. In some auditoria, spatial variation in IAQ was identified, indicating poor mixing of the air. In addition, surface and air samples were taken and analysed for the presence of bacteria by culture and SARS-CoV-2 using RT-qPCR in one venue. SARS-CoV-2 RNA was detected on a small number of surfaces at very low copy numbers, which are unlikely to pose an infection risk. Under the ventilation strategies and occupancy levels investigated, it is likely that most theatres pose a low risk of long-range transmission of COVID-19.
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Affiliation(s)
- Filipa Adzic
- Department of Civil, Environmental and Geomatic Engineering, University College London, UK
| | - Ben M Roberts
- Building Energy Research Group, School of Architecture, Building and Civil Engineering, Loughborough University, UK
| | | | - Rupy Kaur Matharu
- Department of Civil, Environmental and Geomatic Engineering, University College London, UK
| | - Lena Ciric
- Department of Civil, Environmental and Geomatic Engineering, University College London, UK
| | - Oliver Wild
- Department of Civil, Environmental and Geomatic Engineering, University College London, UK
| | - Malcolm Cook
- Building Energy Research Group, School of Architecture, Building and Civil Engineering, Loughborough University, UK
| | - Liora Malki-Epshtein
- Department of Civil, Environmental and Geomatic Engineering, University College London, UK
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19
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Morawska L, Buonanno G, Mikszewski A, Stabile L. The physics of respiratory particle generation, fate in the air, and inhalation. NATURE REVIEWS. PHYSICS 2022; 4:723-734. [PMID: 36065441 PMCID: PMC9430019 DOI: 10.1038/s42254-022-00506-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 08/03/2022] [Indexed: 05/31/2023]
Abstract
Given that breathing is one of the most fundamental physiological functions, there is an urgent need to broaden our understanding of the fluid dynamics that governs it. There would be many benefits from doing so, including a better assessment of respiratory health, a basis for more precise delivery of pharmaceutical drugs for treatment, and the understanding and potential minimization of respiratory infection transmission. We review the physics of particle generation in the respiratory tract, the fate of these particles in the air on exhalation and the physics of particle inhalation. The main focus is on evidence from experimental studies. We conclude that although there is qualitative understanding of the generation of particles in the respiratory tract, a basic quantitative knowledge of the characteristics of the particles emitted during respiratory activities and their fate after emission, and a theoretical understanding of particle deposition during inhalation, nevertheless the general understanding of the entire process is rudimentary, and many open questions remain.
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Affiliation(s)
- Lidia Morawska
- Queensland University of Technology, International Laboratory for Air Quality & Health (ILAQH), Brisbane, Queensland Australia
- Global Centre for Clean Air Research, Department of Civil and Environmental Engineering, University of Surrey, Guildford, UK
| | - Giorgio Buonanno
- Queensland University of Technology, International Laboratory for Air Quality & Health (ILAQH), Brisbane, Queensland Australia
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, Italy
| | - Alex Mikszewski
- Queensland University of Technology, International Laboratory for Air Quality & Health (ILAQH), Brisbane, Queensland Australia
| | - Luca Stabile
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, Italy
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20
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Ferrari S, Blázquez T, Cardelli R, Puglisi G, Suárez R, Mazzarella L. Ventilation strategies to reduce airborne transmission of viruses in classrooms: A systematic review of scientific literature. BUILDING AND ENVIRONMENT 2022; 222:109366. [PMID: 35818484 PMCID: PMC9259197 DOI: 10.1016/j.buildenv.2022.109366] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 06/20/2022] [Accepted: 07/02/2022] [Indexed: 06/15/2023]
Abstract
The recent pandemic due to SARS-CoV-2 has brought to light the need for strategies to mitigate contagion between human beings. Apart from hygiene measures and social distancing, air ventilation highly prevents airborne transmission within enclosed spaces. Among others, educational environments become critical in strategic planning to control the spread of pathogens and viruses amongst the population, mainly in cold conditions. In the event of a virus outbreak - such as COVID or influenza - many school classrooms still lack the means to guarantee secure and healthy environments. The present review examines school contexts that implement air ventilation strategies to reduce the risk of contagion between students. The analysed articles present past experiences that use either natural or mechanical systems assessed through mathematical models, numerical models, or full-scale experiments. For naturally ventilated classrooms, the studies highlight the importance of the architectural design of educational spaces and propose strategies for aeration control such as CO2-based control and risk-infection control. When it comes to implementing mechanical ventilation in classrooms, different systems with different airflow patterns are assessed based on their ability to remove airborne pathogens considering parameters like the age of air and the generation of airflow streamlines. Moreover, studies report that programmed mechanical ventilation systems can reduce risk-infection during pandemic events. In addition to providing a systematic picture of scientific studies in the field, the findings of this review can be a valuable reference for school administrators and policymakers to implement the best strategies in their classroom settings towards reducing infection risks.
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Affiliation(s)
- S Ferrari
- Dept. of Architecture, Built Environment and Construction Engineering, Politecnico di Milano, Milano, Italy
| | - T Blázquez
- Dept. of Architecture, Built Environment and Construction Engineering, Politecnico di Milano, Milano, Italy
| | - R Cardelli
- Dept. of Architecture, Built Environment and Construction Engineering, Politecnico di Milano, Milano, Italy
| | - G Puglisi
- Dept. of Energy Efficiency Department, Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA), Rome, Italy
| | - R Suárez
- Instituto Universitario de Arquitectura y Ciencias de la Construcción, Escuela Técnica Superior de Arquitectura, Universidad de Sevilla, Sevilla, Spain
| | - L Mazzarella
- Dept. of Energy, Politecnico di Milano, Milano, Italy
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21
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Al-Rawi M, Al-Jumaily AM, Lazonby A. Did You Just Cough? Visualization of Vapor Diffusion in an Office Using Computational Fluid Dynamics Analysis. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2022; 19:9928. [PMID: 36011558 PMCID: PMC9408159 DOI: 10.3390/ijerph19169928] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Revised: 08/05/2022] [Accepted: 08/10/2022] [Indexed: 06/15/2023]
Abstract
Awareness of indoor air quality (IAQ) in crowded places such as schools and offices has increased since 2020 due to the COVID-19 pandemic. In addition, countries' shifting away from containment and towards living with COVID-19 is expected to increase demand for risk mitigation via air-purification devices. In this work, we use Computational Fluid Dynamics (CFD) analysis to investigate the impact of adding an air-purification technology on airflow in an enclosed space. We model a Polyester Filter and UV light (PFUV) dehumidifier in an office with two occupants: one infected with an airborne infectious disease, such as COVID-19; and the other uninfected. We compare three cases where the infected occupant coughs: with no device, and with the device at two different orientations. We construct a CFD model using ANSYS® 2021 Fluent and the Discrete Phase Model (DPM) for the particle treatment. Thermal comfort is assessed using the Testo 400 IAQ and comfort kit. We find that both the device operation and the placement alter the airflow contours, significantly reducing the potential for the uninfected occupant to inhale the vapour expelled by the infected occupant, potentially impacting the likelihood of disease transmission. The device improved thermal comfort measured by Predicted Mean Vote (PMV), Predicted Percentage Dissatisfied (PPD).
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Affiliation(s)
- Mohammad Al-Rawi
- Centre for Engineering and Industrial Design (CEID), Waikato Institute of Technology, Hamilton 3240, New Zealand
| | - Ahmed M. Al-Jumaily
- Institute of Biomedical Technologies (IBTec), Auckland University of Technology (AUT), Auckland 1010, New Zealand
| | - Annette Lazonby
- Faculty of Business and Economics, The University of Auckland, Auckland 1010, New Zealand
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22
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Sarhan AAR, Naser P, Naser J. Numerical study of when and who will get infected by coronavirus in passenger car. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2022; 29:57232-57247. [PMID: 35349056 PMCID: PMC8960670 DOI: 10.1007/s11356-022-19824-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Accepted: 03/16/2022] [Indexed: 05/30/2023]
Abstract
In light of the COVID-19 pandemic, it is becoming extremely necessary to assess respiratory disease transmission in passenger cars. This study numerically investigated the human respiration activities' effects, such as breathing and speaking, on the transport characteristics of respiratory-induced contaminants in passenger car. The main objective of the present study is to accurately predict when and who will get infected by coronavirus while sharing a passenger car with a patient of COVID-19 or similar viruses. To achieve this goal, transient simulations were conducted in passenger car. We conducted a 3D computational fluid dynamics (CFD)-based investigation of indoor airflow and the associated aerosol transport in a passenger car. The Eulerian-Eulerian flow model coupled with k-ε turbulence approach was used to track respiratory contaminants with diameter ≥ 1 μm that were released by different passengers within the passenger car. The results showed that around 6.38 min, this is all that you need to get infected with COVID-19 when sharing a poorly ventilated car with a driver who got coronavirus. It also has been found that enhancing the ventilation system of the passenger car will reduce the risk of contracting Coronavirus. The predicted results could be useful for future engineering studies aimed at designing public transport and passenger cars to face the spread of droplets that may be contaminated with pathogens.
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Affiliation(s)
- Abd Alhamid R Sarhan
- Department of Mechanical and Product Design Engineering, Swinburne University of Technology, Hawthorn, VIC, 3122, Australia.
| | - Parisa Naser
- Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 21205, USA
| | - Jamal Naser
- Department of Mechanical and Product Design Engineering, Swinburne University of Technology, Hawthorn, VIC, 3122, Australia
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23
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Li Y, Wu C, Cao G, Guan D, Zhan C. Transmission characteristics of respiratory droplets aerosol in indoor environment: an experimental study. INTERNATIONAL JOURNAL OF ENVIRONMENTAL HEALTH RESEARCH 2022; 32:1768-1779. [PMID: 33825604 DOI: 10.1080/09603123.2021.1910629] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Accepted: 03/25/2021] [Indexed: 06/12/2023]
Abstract
Transmission of droplets has been recognized as an important form of infection for the respiratory diseases. This study investigated the distribution of human respiratory droplets and assessed the effects of air change rate and generated velocity on droplet transmission using an active agent in an enclosed chamber (46 m3). Results revealed that the higher the air change rate was, the fewer viable droplets were detected in the range of <3.3 μm with ventilation; an increased air change rate can increase the attenuation of droplet aerosol. Without ventilation, the viable droplet size was observed to mainly distribute greater than 3.3 μm, which occupied up 87.5% of the total number. When the generated velocity was increased to 20 m/s, 29.38% of the viable droplets were detected at the position of 2.0 m. The findings are excepted to be useful for developing the technology of reducing droplet propagation and providing data verification for simulation research.
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Affiliation(s)
- Yanju Li
- School of Energy and Safety Engineering, Tianjin Chengjian University, Tianjin, China
| | - Chunbin Wu
- School of Energy and Safety Engineering, Tianjin Chengjian University, Tianjin, China
| | - Guoqing Cao
- Institute of Building Environment and Energy, China Academy of Building Research, Beijing, China
| | - Dexing Guan
- School of Energy and Safety Engineering, Tianjin Chengjian University, Tianjin, China
| | - Chaoguo Zhan
- School of Environmental Science and Safety Engineering, Tianjin University of Technology, Tianjin, China
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24
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Gulec F, Atakan B, Dressler F. Mobile human ad hoc networks: A communication engineering viewpoint on interhuman airborne pathogen transmission. NANO COMMUNICATION NETWORKS 2022; 32:100410. [PMID: 35996611 PMCID: PMC9385271 DOI: 10.1016/j.nancom.2022.100410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/02/2022] [Revised: 08/03/2022] [Accepted: 08/14/2022] [Indexed: 06/15/2023]
Abstract
A number of transmission models for airborne pathogens transmission, as required to understand airborne infectious diseases such as COVID-19, have been proposed independently from each other, at different scales, and by researchers from various disciplines. We propose a communication engineering approach that blends different disciplines such as epidemiology, biology, medicine, and fluid dynamics. The aim is to present a unified framework using communication engineering, and to highlight future research directions for modeling the spread of infectious diseases through airborne transmission. We introduce the concept of mobile human ad hoc networks (MoHANETs), which exploits the similarity of airborne transmission-driven human groups with mobile ad hoc networks and uses molecular communication as the enabling paradigm. In the MoHANET architecture, a layered structure is employed where the infectious human emitting pathogen-laden droplets and the exposed human to these droplets are considered as the transmitter and receiver, respectively. Our proof-of-concept results, which we validated using empirical COVID-19 data, clearly demonstrate the ability of our MoHANET architecture to predict the dynamics of infectious diseases by considering the propagation of pathogen-laden droplets, their reception and mobility of humans.
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Affiliation(s)
- Fatih Gulec
- School of Electrical Engineering and Computer Science, TU Berlin, Germany
- Izmir Institute of Technology, Department of Electrical and Electronics Engineering, Izmir, Turkey
| | - Baris Atakan
- Izmir Institute of Technology, Department of Electrical and Electronics Engineering, Izmir, Turkey
| | - Falko Dressler
- School of Electrical Engineering and Computer Science, TU Berlin, Germany
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25
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Aerodynamic Prediction of Time Duration to Becoming Infected with Coronavirus in a Public Place. FLUIDS 2022. [DOI: 10.3390/fluids7050176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The COVID-19 pandemic has caused panic and chaos that modern society has never seen before. Despite their paramount importance, the transmission routes of coronavirus SARS-CoV-2 remain unclear and a point of contention between the various sectors. Recent studies strongly suggest that COVID-19 could be transmitted via air in inadequately ventilated environments. The present study investigates the possibility of the aerosol transmission of coronavirus SARS-CoV-2 and illustrates the associated environmental conditions. The main objective of the current work is to accurately predict the time duration of getting an infection while sharing an indoor space with a patient of COVID-19 or similar viruses. We conducted a 3D computational fluid dynamics (CFD)-based investigation of indoor airflow and the associated aerosol transport in a restaurant setting, where likely cases of airflow-induced infection of COVID-19 caused by asymptomatic individuals were reported in Guangzhou, China. The Eulerian–Eulerian flow model coupled with the k-Ɛ turbulence approach was employed to resolve complex indoor processes, including human respiration activities, such as breathing, speaking, and sneezing. The predicted results suggest that 10 minutes are enough to become infected with COVID-19 when sharing a Table with coronavirus patients. The results also showed that although changing the ventilation rate will improve the quality of air within closed spaces, it will not be enough to protect a person from COVID-19. This model may be suitable for future engineering analyses aimed at reshaping public spaces and indoor common areas to face the spread of aerosols and droplets that may contain pathogens.
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Fan M, Fu Z, Wang J, Wang Z, Suo H, Kong X, Li H. A review of different ventilation modes on thermal comfort, air quality and virus spread control. BUILDING AND ENVIRONMENT 2022; 212:108831. [PMID: 35125624 PMCID: PMC8799382 DOI: 10.1016/j.buildenv.2022.108831] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 01/11/2022] [Accepted: 01/21/2022] [Indexed: 05/12/2023]
Abstract
In the era of Corona Virus Disease 2019 (COVID-19), inappropriate indoor ventilation may turn out to be the culprit of microbial contamination in enclosed spaces and deteriorate the environment. To collaboratively improve the thermal comfort, air quality and virus spread control effect, it was essential to have an overall understanding of different ventilation modes. Hence, this study reviewed the latest scientific literature on indoor ventilation modes and manuals of various countries, identified characteristics of different ventilation modes and evaluated effects in different application occasions, wherefore to further propose their main limitations and solutions in the epidemic era. For thermal comfort, various non-uniform ventilation modes could decrease the floor-to-ceiling temperature difference, draft rate or PPD by 60%, 80% or 33% respectively, or increase the PMV by 45%. Unsteady ventilation modes (including intermittent ventilation and pulsating ventilation) could lower PPD values by 12%-37.8%. While for air quality and virus spread control, non-uniform ventilation modes could lower the mean age of air or contaminants concentration by 28.3%-47% or 15%-47% respectively, increase the air change efficiency, contaminant removal effectiveness or protection efficiency by 6.6%-10.4%, 22.6% or 14%-50% respectively. Unsteady ventilation mode (pulsating ventilation) could reduce the peak pollutant concentration and exposure time to undesirable concentrations by 31% and 48% respectively. Non-uniform modes and unsteady modes presented better performance in thermal comfort, air quality and virus spread control, whereas relevant performance evaluation indexes were still imperfect and the application scenarios were also limited.
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Affiliation(s)
- Man Fan
- School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin, 300401, China
| | - Zheng Fu
- School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin, 300401, China
| | - Jia Wang
- School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin, 300401, China
| | - Zhaoying Wang
- School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin, 300401, China
| | - Hanxiao Suo
- School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin, 300401, China
| | - Xiangfei Kong
- School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin, 300401, China
| | - Han Li
- School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin, 300401, China
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Leonardi AJ, Mishra AK. A Sanitation Argument for Clean Indoor Air: Meeting a Requisite for Safe Public Spaces. Front Public Health 2022; 10:805780. [PMID: 35237550 PMCID: PMC8883285 DOI: 10.3389/fpubh.2022.805780] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Accepted: 01/06/2022] [Indexed: 11/13/2022] Open
Affiliation(s)
| | - Asit Kumar Mishra
- MaREI Centre, Ryan Institute & School of Engineering, College of Science and Engineering, National University of Ireland Galway, Galway, Ireland
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Mohamadi F, Fazeli A. A Review on Applications of CFD Modeling in COVID-19 Pandemic. ARCHIVES OF COMPUTATIONAL METHODS IN ENGINEERING : STATE OF THE ART REVIEWS 2022; 29:3567-3586. [PMID: 35079217 PMCID: PMC8773396 DOI: 10.1007/s11831-021-09706-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Accepted: 12/28/2021] [Indexed: 05/25/2023]
Abstract
COVID-19 pandemic has started a big challenge to the world health and economy during recent years. Many efforts were made to use the computation fluid dynamic (CFD) approach in this pandemic. CFD was used to understanding the airborne dispersion and transmission of this virus in different situations and buildings. The effect of the different conditions of the ventilation was studied by the CFD modeling to discuss preventing the COVID-19 transmission. Social distancing and using the facial masks were also modeled by the CFD approach to study the effect on reducing dispersion of the microdroplets containing the virus. Most of these recent applications of the CFD were reviewed for COVID-19 in this article. Special applications of the CFD modeling such as COVID-19 microfluidic biosensors, and COVID-19 inactivation using UV radiation were also reviewed in this research. The main findings of each research were also summarized in a table to answer critical questions about the effectiveness levels of applying the COVID-19 health protocols. CFD applications for modeling of COVID-19 dispersion in an airplane cabin, an elevator, a small classroom, a supermarket, an operating room of a hospital, a restaurant, a hospital waiting room, and a children's recovery room in a hospital were discussed briefly in different scenarios. CFD modeling for studying the effect of social distancing with different spaces, using and not using facial masks, difference of sneezing and coughing, different inlet/outlet ventilation layouts, combining air-conditioning and sanitizing machine, and using general or local air-conditioning systems were reviewed.
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Affiliation(s)
- Fateme Mohamadi
- Department of Chemical Engineering, Caspian Faculty of Engineering, College of Engineering, University of Tehran, Tehran, Iran
| | - Ali Fazeli
- Department of Chemical Engineering, Caspian Faculty of Engineering, College of Engineering, University of Tehran, Tehran, Iran
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Vardoulakis S, Espinoza Oyarce DA, Donner E. Transmission of COVID-19 and other infectious diseases in public washrooms: A systematic review. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 803:149932. [PMID: 34525681 PMCID: PMC8390098 DOI: 10.1016/j.scitotenv.2021.149932] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 08/13/2021] [Accepted: 08/23/2021] [Indexed: 05/03/2023]
Abstract
BACKGROUND The risk of infectious disease transmission in public washrooms causes concern particularly in the context of the COVID-19 pandemic. This systematic review aims to assess the risk of transmission of viral or bacterial infections through inhalation, surface contact, and faecal-oral routes in public washrooms in healthcare and non-healthcare environments. METHODS We systematically reviewed environmental sampling, laboratory, and epidemiological studies on viral and bacterial infection transmission in washrooms using PubMed and Scopus. The review focused on indoor, publicly accessible washrooms. RESULTS Thirty-eight studies from 13 countries were identified, including 14 studies carried out in healthcare settings, 10 in laboratories or experimental chambers, and 14 studies in restaurants, workplaces, commercial and academic environments. Thirty-three studies involved surface sampling, 15 air sampling, 8 water sampling, and 5 studies were risk assessments or outbreak investigations. Infectious disease transmission was studied in relation with: (a) toilets with flushing mechanisms; (b) hand drying systems; and (c) water taps, sinks and drains. A wide range of enteric, skin and soil bacteria and enteric and respiratory viruses were identified in public washrooms, potentially posing a risk of infection transmission. Studies on COVID-19 transmission only examined washroom contamination in healthcare settings. CONCLUSION Open-lid toilet flushing, ineffective handwashing or hand drying, substandard or infrequent surface cleaning, blocked drains, and uncovered rubbish bins can result in widespread bacterial and/or viral contamination in washrooms. However, only a few cases of infectious diseases mostly related to faecal-oral transmission originating from washrooms in restaurants were reported. Although there is a risk of microbial aerosolisation from toilet flushing and the use of hand drying systems, we found no evidence of airborne transmission of enteric or respiratory pathogens, including COVID-19, in public washrooms. Appropriate hand hygiene, surface cleaning and disinfection, and washroom maintenance and ventilation are likely to minimise the risk of infectious disease transmission.
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Affiliation(s)
- Sotiris Vardoulakis
- National Centre for Epidemiology and Population Health, Research School of Population Health, Australian National University, Canberra, ACT 2601, Australia.
| | - Daniela A Espinoza Oyarce
- National Centre for Epidemiology and Population Health, Research School of Population Health, Australian National University, Canberra, ACT 2601, Australia
| | - Erica Donner
- Future Industries Institute, University of South Australia, Mawson Lakes, SA 5095, Australia
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Xu J, Wang C, Fu SC, Chao CYH. The effect of head orientation and personalized ventilation on bioaerosol deposition from a cough. INDOOR AIR 2022; 32:e12973. [PMID: 34888956 DOI: 10.1111/ina.12973] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 11/29/2021] [Accepted: 12/01/2021] [Indexed: 06/13/2023]
Abstract
Head orientations directly determine movement directions of exhaled pathogen-laden droplets, while there is a lack of research about the effect of the infected person's head orientations on respiratory disease transmission during close contact. This work experimentally investigated the effect of different head orientations of an infected person (IP) on the bioaerosol deposition on a healthy person (HP) during close contact. Also, the effectiveness of PV flow in reducing bioaerosol deposition on the HP under the IP's different head orientations was investigated. Bacteriophage T3 was employed to represent viruses inside the cough-generated aerosols. The bioaerosol depositions on different locations of the HP's upper body (chest, shoulder, and neck) and face (chin, mucous membranes, cheek, and forehead) were characterized by a cultivation method. Results showed that the IP's different head orientations resulted in significantly different deposition density on the HP. PV flow could reduce the bioaerosol deposition remarkably for most cases investigated. The effectiveness of PV flow in reducing deposition on the HP was significantly affected by the IP's head orientations. Findings suggest that changing head orientations can be a control measure to reduce the bioaerosol deposition. Personalized ventilation can be a potential method to reduce the bioaerosol deposition on the HP.
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Affiliation(s)
- Jingcui Xu
- Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Hong Kong, China
- Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong, China
| | - Cunteng Wang
- Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Hong Kong, China
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China
| | - Sau Chung Fu
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China
| | - Christopher Y H Chao
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China
- Department of Building Environment and Energy Engineering, Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hong Kong, China
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31
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Mehade Hussain S, Goel S, Kadapa C, Aristodemou E. A short review of vapour droplet dispersion models used in CFD to study the airborne spread of COVID19. MATERIALS TODAY: PROCEEDINGS 2022; 64:1349-1356. [PMID: 35495177 PMCID: PMC9035368 DOI: 10.1016/j.matpr.2022.03.724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The use of computational fluid dynamics (CFD) to simulate the spread of COVID19 and many other airborne diseases, especially in an indoor environment needs accurate understanding of dispersion models. Modelling the transport/dispersion of vapour droplets within the atmosphere is a complex problem, as it involves the motion of more than one phase, as well as the interphase interactions between the phases. This paper reviews the current canon of research on dispersion modelling of vapour droplets by looking at three specific aspects: (i) physical definition/specification of the initial droplet size distribution; (ii) physics of evaporation/condensation models and (iii) transport equations (with molecular/turbulent dispersion models) to describe the movement of the vapour droplets as they propagate through the air. This review found that the state of modelling implements a wide range of models which shows variances in results thus leading to a state where it is difficult to know which model is most accurate. The authors suggest that further studies in this direction should focus on developing a principle set of equations by benchmarking the previously developed models to establish model uncertainty of the previously developed models with reference to a fixed theoretical model and be compared under identical conditions. However, it must be noted that due to the complex nature of microdroplet evaporation and dispersion coupled with the unpredictable way droplet size distributions are produced, current experimental methodologies that are available to validate such simulations, such as particle image velocimetry, are still not robust enough to provide detailed data to verify minute aspects of the simulations.
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Affiliation(s)
| | - Saurav Goel
- School of Engineering, London South Bank University, London SE10 AA, UK
- University of Petroleum and Energy Studies, Dehradun 248007, India
- Indian Institute of Technology Guwahati, Guwahati 781039, India
| | | | - Elsa Aristodemou
- School of Engineering, London South Bank University, London SE10 AA, UK
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32
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Bueno de Mesquita PJ, Delp WW, Chan WR, Bahnfleth WP, Singer BC. Control of airborne infectious disease in buildings: Evidence and research priorities. INDOOR AIR 2022; 32:e12965. [PMID: 34816493 DOI: 10.1111/ina.12965] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Revised: 10/07/2021] [Accepted: 11/11/2021] [Indexed: 06/13/2023]
Abstract
The evolution of SARS-CoV-2 virus has resulted in variants likely to be more readily transmitted through respiratory aerosols, underscoring the increased potential for indoor environmental controls to mitigate risk. Use of tight-fitting face masks to trap infectious aerosol in exhaled breath and reduce inhalation exposure to contaminated air is of critical importance for disease control. Administrative controls including the regulation of occupancy and interpersonal spacing are also important, while presenting social and economic challenges. Indoor engineering controls including ventilation, exhaust, air flow control, filtration, and disinfection by germicidal ultraviolet irradiation can reduce reliance on stringent occupancy restrictions. However, the effects of controls-individually and in combination-on reducing infectious aerosol transfer indoors remain to be clearly characterized to the extent needed to support widespread implementation by building operators. We review aerobiologic and epidemiologic evidence of indoor environmental controls against transmission and present a quantitative aerosol transfer scenario illustrating relative differences in exposure at close-interactive, room, and building scales. We identify an overarching need for investment to implement building controls and evaluate their effectiveness on infection in well-characterized and real-world settings, supported by specific, methodological advances. Improved understanding of engineering control effectiveness guides implementation at scale while considering occupant comfort, operational challenges, and energy costs.
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Affiliation(s)
| | - William W Delp
- Indoor Environment Group, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Wanyu R Chan
- Indoor Environment Group, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - William P Bahnfleth
- Department of Architectural Engineering, Pennsylvania State University, State College, Pennsylvania, USA
| | - Brett C Singer
- Indoor Environment Group, Lawrence Berkeley National Laboratory, Berkeley, California, USA
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33
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Fu L, Yang M, Niu J, Ren W, You R. Transient tracer gas measurements: Development and evaluation of a fast-response SF 6 measuring system based on quartz-enhanced photoacoustic spectroscopy. INDOOR AIR 2022; 32:e12952. [PMID: 34747064 DOI: 10.1111/ina.12952] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 10/08/2021] [Accepted: 10/27/2021] [Indexed: 06/13/2023]
Abstract
This study aims to develop a fast-response sulfur hexafluoride (SF6 ) measuring system, and evaluate its performance in tracer gas measurements for studying transient airborne contaminant transport. The new system is based on a quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor using a quantum cascade laser. Transient SF6 tracer gas measurements were carried out in an environmental chamber with an instantaneous source using both the QEPAS system and a traditional commercial instrument. Real-time SF6 concentrations, peak SF6 concentrations and average SF6 concentrations for one room time constant under two air change rates obtained by the two instruments were compared. The results show that the QEPAS system, which features a 0.4 s data acquisition interval, can provide detailed real-time SF6 concentrations even when the concentration is changing rapidly. The QEPAS system successfully captured the peak SF6 concentrations for all the studies cases, while commercial instrument failed in most studied cases. In most of the cases, the two instruments obtained similar average SF6 concentrations for one room time constant. However, when the concentration was in rapid change, the two systems would report significantly different results. The QEPAS system can be potentially applied in transient tracer gas measurements under complex scenarios.
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Affiliation(s)
- Liye Fu
- Department of Building Environment and Energy Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, China
| | - Min Yang
- Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, New Territories, Hong Kong SAR, China
| | - Jianlei Niu
- Department of Building Environment and Energy Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, China
| | - Wei Ren
- Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, New Territories, Hong Kong SAR, China
| | - Ruoyu You
- Department of Building Environment and Energy Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, China
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34
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Liu W, Liu L, Xu C, Fu L, Wang Y, Nielsen PV, Zhang C. Exploring the potentials of personalized ventilation in mitigating airborne infection risk for two closely ranged occupants with different risk assessment models. ENERGY AND BUILDINGS 2021; 253:111531. [PMID: 34611376 PMCID: PMC8483985 DOI: 10.1016/j.enbuild.2021.111531] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Revised: 09/20/2021] [Accepted: 09/28/2021] [Indexed: 05/15/2023]
Abstract
In the context of COVID-19, new requirements are occurring in ventilation systems to mitigate airborne transmission risk in indoor environment. Personalized ventilation (PV) which directly delivers clean air to the occupant's breathing zone is considered as a promising solution. To explore the potentials of PV in preventing the spread of infectious aerosols between closely ranged occupants, experiments were conducted with two breathing thermal manikins with three different relative orientations. Nebulized aerosols were used to mimic exhaled droplets transmitted between the occupants. Four risk assessment models were applied to evaluate the exposure or infection risk affected by PV with different operation modes. Results show that PV was effective in reducing the user's infection risk compared with mixing ventilation alone. Relative orientations and operation modes of PV significantly affected its performance in airborne risk control. The infection risk of SARS-CoV-2 was reduced by 65% with PV of 9 L/s after an exposure duration of 2 h back-to-back as assessed by the dose-response model, indicating effective protection effect of PV against airborne transmission. While the side-by-side orientation was found to be the most critical condition for PV in airborne risk control as it would accelerate diffusion of infectious droplets in lateral diffusion to occupants by side. Optimal designs of PV for closely ranged occupants were hereby discussed. The four risk assessment models were compared and validated by experiments with PV, implying basically consistent rules of the predicted risk with PV among the four models. The relevance and applicability of these models were discussed to provide a basis for risk assessment with non-uniformly distributed pathogens indoor.
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Affiliation(s)
- Wenbing Liu
- College of Pipeline and Civil Engineering, China University of Petroleum, Qingdao 266580, China
| | - Li Liu
- Department of Building Science, School of Architecture, Tsinghua University, Beijing 100084, China
- State Key Laboratory of Green Building in Western China, Xian University of Architecture & Technology, Xi'an 710055, China
- Laboratory of Eco-Planning & Green Building, Ministry of Education, Tsinghua University, Beijing 100084, China
| | - Chunwen Xu
- College of Pipeline and Civil Engineering, China University of Petroleum, Qingdao 266580, China
| | - Linzhi Fu
- State Key Laboratory of Green Building in Western China, Xian University of Architecture & Technology, Xi'an 710055, China
| | - Yi Wang
- State Key Laboratory of Green Building in Western China, Xian University of Architecture & Technology, Xi'an 710055, China
| | - Peter V Nielsen
- Division of Sustainability, Energy and Indoor Environment, Aalborg University, Aalborg 9000, Denmark
| | - Chen Zhang
- Division of Sustainability, Energy and Indoor Environment, Aalborg University, Aalborg 9000, Denmark
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Influence of ambient conditions on evaporation and transport of respiratory droplets in indoor environment. INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER 2021; 129. [PMCID: PMC8577817 DOI: 10.1016/j.icheatmasstransfer.2021.105750] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Respiratory droplets are playing a significant role in the transmission of any flu type disease as well as SARS-Cov-2 virus. The presence of pathogens affects the evaporation of the liquid droplets along with ambient temperature and relative humidity (rh). Complete evaporation of droplets leads to the formation of aerosol or droplet nuclei which remain suspended in the air for a longer period of time and get spread over larger distances increasing the risk of disease transmission. In present work, a droplet evaporation model has been formulated considering the droplet as a salt solution and the formation of crystals has been taken into account which will be analogous to the aerosol formation. After the establishment of the evaporation model, the trajectories of the droplets are investigated considering a turbulent round jet model during exhalation. Aerosols are found to be spreading over distances of 8 to 9 m which is quite alarming. Large droplets get converted to smaller ones but the viral loading of the large droplets is much higher than the smaller as viral loading is proportional to initial size. This is highlighted by the viral load contour and the mean diameter line contour for a half-height window. Different weather conditions are investigated to observe the evaporation of droplets and the formation of aerosols in order to qualitatively analyse the risks associated with each city in specific weather conditions. Hot and dry conditions are most favourable to aerosol formation.
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36
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Senerat AM, Pope ZC, Rydell SA, Mullan AF, Roger VL, Pereira MA. Psychosocial and Behavioral Outcomes and Transmission Prevention Behaviors: Working During the Coronavirus Disease 2019 Pandemic. Mayo Clin Proc Innov Qual Outcomes 2021; 5:1089-1099. [PMID: 34485827 PMCID: PMC8397528 DOI: 10.1016/j.mayocpiqo.2021.08.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
OBJECTIVE To investigate the impact of coronavirus disease 2019 (COVID-19) on psychosocial and behavioral responses of the non-health care workforce and to evaluate transmission prevention behavior implementation in the workplace. PARTICIPANTS AND METHODS We deployed the baseline questionnaire of a prospective online survey from November 20, 2020, through February 8, 2021 to US-based employees. The survey included questions on psychosocial and behavioral responses in addition to transmission prevention behaviors (e.g., mask wearing). Select questions asked employees to report perceptions and behaviors before and during the COVID-19 pandemic. Data were analyzed descriptively and stratified by work from home (WFH) percentage. RESULTS In total, 3607 employees from 8 companies completed the survey. Most participants (70.0%) averaged 90% or more of their time WFH during the pandemic. Employees reported increases in stress (54.0%), anxiety (57.4%), fatigue (51.6%), feeling unsafe (50.4%), lack of companionship (60.5%), and feeling isolated from others (69.3%) from before to during the pandemic. Productivity was perceived to decrease for 42.9% of employees and non-work-related screen time and alcohol consumption to increase for 50.7% and 25.1% of employees, respectively, from before to during the pandemic. Adverse changes were worse among those with lower WFH percentages. Most employees reported wearing a mask (98.2%), washing hands regularly (95.7%), and physically distancing (93.6%) in the workplace. CONCLUSION These results suggest worsened psychosocial and behavioral outcomes from before to during the COVID-19 pandemic and higher transmission prevention behavior implementation among non-health care employees. These observations provide novel insight into how the COVID-19 pandemic has impacted non-health care employees.
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Affiliation(s)
| | - Zachary C. Pope
- Well Living Lab, Rochester, MN
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN
| | - Sarah A. Rydell
- Division of Epidemiology and Community Health, University of Minnesota, Minneapolis, MN
| | - Aidan F. Mullan
- Department of Quantitative Health Sciences, Mayo Clinic, Rochester, MN
| | - Véronique L. Roger
- Department of Cardiovascular Diseases Medicine, Mayo Clinic College of Medicine, Rochester, MN
- Now with the Epidemiology and Community Health Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD
| | - Mark A. Pereira
- Division of Epidemiology and Community Health, University of Minnesota, Minneapolis, MN
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37
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Sarhan AR, Naser P, Naser J. COVID-19 aerodynamic evaluation of social distancing in indoor environments, a numerical study. JOURNAL OF ENVIRONMENTAL HEALTH SCIENCE & ENGINEERING 2021; 19:1969-1978. [PMID: 34721881 PMCID: PMC8542656 DOI: 10.1007/s40201-021-00748-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Accepted: 10/17/2021] [Indexed: 06/13/2023]
Abstract
PURPOSE Many countries worldwide have taken early measures to combat the spread of coronavirus SARS-CoV-2 by implementing social distancing measures. The main aim of the present work is to examine the feasibility of social distancing (i.e. 1.5 m) in closed spaces taking into account the possibility for airborne transmission of SARS-CoV-2. METHODS A 3D numerical model of human respiration activities, such as breathing and speaking within indoor environments has been simulated with CFD software AVL FIRE R2020. The Eulerian-Eulerian flow model coupled with k-Ɛ approach were employed. With regard to breathing mode, the infected individual is modelled to be breathing 10 times per minute with a pulmonary rate of 6 L/min with a sinusoidal cycle. The present investigation considered air and droplets/particles as separate phases. RESULTS The predicted results suggested that the social distancing (i.e. 1.5 m) is not adequate to reduce the risk of contracting diseases like COVID-19, especially when staying for a longer period in an indoor environment. The person directly facing the infected person inhaled more than 1000 aerosol droplets within 30 min. The results also showed approximately 65 % decrease in the number of inhaled droplets the room is well ventilated. CONCLUSIONS Within an indoor environment, 1.5 m distance will not be enough to protect the healthy individuals from the droplets coming from an infected person. Also, the situation may become worse with the change of the air ventilation system.
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Affiliation(s)
- A. R. Sarhan
- Department of Mechanical and Product Design Engineering, Swinburne University of Technology, Hawthorn, Victoria 3122 Australia
| | - P. Naser
- Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205 USA
| | - J. Naser
- Department of Mechanical and Product Design Engineering, Swinburne University of Technology, Hawthorn, Victoria 3122 Australia
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38
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Cortellessa G, Stabile L, Arpino F, Faleiros DE, van den Bos W, Morawska L, Buonanno G. Close proximity risk assessment for SARS-CoV-2 infection. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 794:148749. [PMID: 34225157 PMCID: PMC8242194 DOI: 10.1016/j.scitotenv.2021.148749] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 06/23/2021] [Accepted: 06/25/2021] [Indexed: 05/04/2023]
Abstract
Although the interpersonal distance represents an important parameter affecting the risk of infection due to respiratory viruses, the mechanism of exposure to exhaled droplets remains insufficiently characterized. In this study, an integrated risk assessment is presented for SARS-CoV-2 close proximity exposure between a speaking infectious subject and a susceptible subject. It is based on a three-dimensional transient numerical model for the description of exhaled droplet spread once emitted by a speaking person, coupled with a recently proposed SARS-CoV-2 emission approach. Particle image velocimetry measurements were conducted to validate the numerical model. The contribution of the large droplets to the risk is barely noticeable only for distances well below 0.6 m, whereas it drops to zero for greater distances where it depends only on airborne droplets. In particular, for short exposures (10 s) a minimum safety distance of 0.75 m should be maintained to lower the risk below 0.1%; for exposures of 1 and 15 min this distance increases to about 1.1 and 1.5 m, respectively. Based on the interpersonal distances across countries reported as a function of interacting individuals, cultural differences, and environmental and sociopsychological factors, the approach presented here revealed that, in addition to intimate and personal distances, particular attention must be paid to exposures longer than 1 min within social distances (of about 1 m).
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Affiliation(s)
- G Cortellessa
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, FR, Italy
| | - L Stabile
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, FR, Italy
| | - F Arpino
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, FR, Italy
| | - D E Faleiros
- Maritime and Transport Technology, TU Delft, Netherlands
| | - W van den Bos
- Maritime and Transport Technology, TU Delft, Netherlands
| | - L Morawska
- International Laboratory for Air Quality and Health, Queensland University of Technology, Brisbane, Qld, Australia
| | - G Buonanno
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, FR, Italy; International Laboratory for Air Quality and Health, Queensland University of Technology, Brisbane, Qld, Australia.
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39
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Cammarata A, Cammarata G. Dynamic assessment of the risk of airborne viral infection. INDOOR AIR 2021; 31:1759-1775. [PMID: 34212441 PMCID: PMC8597137 DOI: 10.1111/ina.12862] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Revised: 05/08/2021] [Accepted: 05/09/2021] [Indexed: 05/24/2023]
Abstract
This paper applies the Rudnick and Milton method through the dynamic evaluation of the probability of airborne contagion, redefining all parameters and variables in discretized form. To adapt the calculation of the risk of contagion to real needs, scenarios are used to define the presence of people, infected subjects, the hourly production of the quanta of infection, and the calculation of the concentration of CO2 produced by exhalation in the air. Three case studies are discussed: a school, an office, a commercial activity. Complex scenarios include environmental sanitization, a variable number of people, and the possibility of simulating work shifts. The dynamic evaluation of the quanta of infection is also estimated, not foreseen by the Rudnick and Milton model, and involves updating the average values of the equivalent fraction of the indoor air with an improvement in the accuracy of the calculation due to the reduction of improper peaks of the stationary variables.
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Affiliation(s)
- Alessandro Cammarata
- Dipartimento di Ingegneria Civile e ArchitetturaUniverità degli Studi di CataniaCataniaItaly
| | - Giuliano Cammarata
- Dipartimento di Ingegneria Elettrica, Elettronica e InformaticaUniverità degli Studi di CataniaCataniaItaly
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40
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Bu Y, Ooka R, Kikumoto H, Oh W. Recent research on expiratory particles in respiratory viral infection and control strategies: A review. SUSTAINABLE CITIES AND SOCIETY 2021; 73:103106. [PMID: 34306994 PMCID: PMC8272400 DOI: 10.1016/j.scs.2021.103106] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 06/07/2021] [Accepted: 06/15/2021] [Indexed: 05/15/2023]
Abstract
The global spread of coronavirus disease 2019 poses a significant threat to human health. In this study, recent research on the characteristics of expiratory particles and flow is reviewed, with a special focus on different respiratory activities, to provide guidance for reducing the viral infection risk in the built environment. Furthermore, environmental influence on particle evaporation, dispersion, and virus viability after exhalation and the current methods for infection risk assessment are reviewed. Finally, we summarize promising control strategies against infectious expiratory particles. The results show that airborne transmission is a significant viral transmission route, both in short and long ranges, from infected individuals. Relative humidity affects the evaporation and trajectories of middle-sized droplets most, and temperature accelerates the inactivation of SARS-CoV-2 both on surfaces and in aerosols. Future research is needed to improve infection risk models to better predict the infection potential of different transmission routes. Moreover, further quantitative studies on the expiratory flow features after wearing a mask are needed. Systematic investigations and the design of advanced air distribution methods, portable air cleaners, and ultraviolet germicidal irradiation systems, which have shown high efficacy in removing contaminants, are required to better control indoor viral infection.
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Affiliation(s)
- Yunchen Bu
- Graduate School of Engineering, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
| | - Ryozo Ooka
- Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
| | - Hideki Kikumoto
- Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
| | - Wonseok Oh
- Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan
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41
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Kurabuchi T, Yanagi U, Ogata M, Otsuka M, Kagi N, Yamamoto Y, Hayashi M, Tanabe S. Operation of air‐conditioning and sanitary equipment for SARS‐CoV‐2 infectious disease control. JAPAN ARCHITECTURAL REVIEW 2021; 4:608-620. [PMCID: PMC8420534 DOI: 10.1002/2475-8876.12238] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Accepted: 06/17/2021] [Indexed: 06/15/2023]
Abstract
It is still undetermined if the main infection route of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), the virus that leads to coronavirus disease 2019 (COVID‐19), is infection through droplet, contact, or airborne transmission. However, confined spaces with poor ventilation are cited as a risk factor for group outbreaks, and there is growing interest in the effects of intervention through the appropriate operation of air‐conditioning and sanitary equipment to reduce the risk of airborne transmission. This study first offers an outline of the characteristics of the novel coronavirus disease and the cluster outbreak case reports that have been clarified until now. Subsequently, we describe the appropriate operating conditions for building equipment that are effective in reducing the risk of infection and also highlight specificities for each building use based on the guidance provided by healthcare institutions and with reference to the standard recommendations by Western academic societies related to building equipment.
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Affiliation(s)
- Takashi Kurabuchi
- Department of ArchitectureFaculty of EngineeringTokyo University of ScienceTokyoJapan
| | - U. Yanagi
- School of ArchitectureKogakuin UniversityTokyoJapan
| | - Masayuki Ogata
- Department of ArchitectureFaculty of Urban Environmental SciencesTokyo Metropolitan UniversityTokyoJapan
| | - Masayuki Otsuka
- College of Architecture and Environmental DesignKanto Gakuin UniversityYokohamaJapan
| | - Naoki Kagi
- School of Environment and SocietyTokyo Institute of TechnologyTokyoJapan
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42
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Pourfattah F, Wang LP, Deng W, Ma YF, Hu L, Yang B. Challenges in simulating and modeling the airborne virus transmission: A state-of-the-art review. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2021; 33:101302. [PMID: 34803360 PMCID: PMC8597718 DOI: 10.1063/5.0061469] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2021] [Accepted: 10/04/2021] [Indexed: 06/09/2023]
Abstract
Recently, the COVID-19 virus pandemic has led to many studies on the airborne transmission of expiratory droplets. While limited experiments and on-site measurements offer qualitative indication of potential virus spread rates and the level of transmission risk, the quantitative understanding and mechanistic insights also indispensably come from careful theoretical modeling and numerical simulation efforts around which a surge of research papers has emerged. However, due to the highly interdisciplinary nature of the topic, numerical simulations of the airborne spread of expiratory droplets face serious challenges. It is essential to examine the assumptions and simplifications made in the existing modeling and simulations, which will be reviewed carefully here to better advance the fidelity of numerical results when compared to the reality. So far, existing review papers have focused on discussing the simulation results without questioning or comparing the model assumptions. This review paper focuses instead on the details of the model simplifications used in the numerical methods and how to properly incorporate important processes associated with respiratory droplet transmission. Specifically, the critical issues reviewed here include modeling of the respiratory droplet evaporation, droplet size distribution, and time-dependent velocity profile of air exhaled from coughing and sneezing. According to the literature review, another problem in numerical simulations is that the virus decay rate and suspended viable viral dose are often not incorporated; therefore here, empirical relationships for the bioactivity of coronavirus are presented. It is hoped that this paper can assist researchers to significantly improve their model fidelity when simulating respiratory droplet transmission.
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Affiliation(s)
- Farzad Pourfattah
- Guangdong Provincial Key Laboratory of Turbulence Research and Applications, Center for Complex Flows and Soft Matter Research and Department of Mechanics and Aerospace Engineering, Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
| | | | - Weiwei Deng
- Guangdong Provincial Key Laboratory of Turbulence Research and Applications, Center for Complex Flows and Soft Matter Research and Department of Mechanics and Aerospace Engineering, Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
| | - Yong-Feng Ma
- Guangdong Provincial Key Laboratory of Turbulence Research and Applications, Center for Complex Flows and Soft Matter Research and Department of Mechanics and Aerospace Engineering, Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
| | - Liangquan Hu
- Guangdong Provincial Key Laboratory of Turbulence Research and Applications, Center for Complex Flows and Soft Matter Research and Department of Mechanics and Aerospace Engineering, Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
| | - Bo Yang
- Guangdong Provincial Key Laboratory of Turbulence Research and Applications, Center for Complex Flows and Soft Matter Research and Department of Mechanics and Aerospace Engineering, Southern University of Science and Technology, Shenzhen 518055, People's Republic of China
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43
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Stabile L, Pacitto A, Mikszewski A, Morawska L, Buonanno G. Ventilation procedures to minimize the airborne transmission of viruses in classrooms. BUILDING AND ENVIRONMENT 2021; 202:108042. [PMID: 34127877 PMCID: PMC8189751 DOI: 10.1016/j.buildenv.2021.108042] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 05/04/2021] [Accepted: 06/05/2021] [Indexed: 05/13/2023]
Abstract
Reducing the transmission of SARS-CoV-2 through indoor air is the key challenge of the COVID-19 pandemic. Crowded indoor environments, such as schools, represent possible hotspots for virus transmission since the basic non-pharmaceutical mitigation measures applied so far (e.g. social distancing) do not eliminate the airborne transmission mode. There is widespread consensus that improved ventilation is needed to minimize the transmission potential of airborne viruses in schools, whether through mechanical systems or ad-hoc manual airing procedures in naturally ventilated buildings. However, there remains significant uncertainty surrounding exactly what ventilation rates are required, and how to best achieve these targets with limited time and resources. This paper uses a mass balance approach to quantify the ability of both mechanical ventilation and ad-hoc airing procedures to mitigate airborne transmission risk in the classroom environment. For naturally-ventilated classrooms, we propose a novel feedback control strategy using CO2 concentrations to continuously monitor and adjust the airing procedure. Our case studies show how such procedures can be applied in the real world to support the reopening of schools during the pandemic. Our results also show the inadequacy of relying on absolute CO2 concentration thresholds as the sole indicator of airborne transmission risk.
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Affiliation(s)
- L Stabile
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, FR, Italy
| | - A Pacitto
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, FR, Italy
| | - A Mikszewski
- International Laboratory for Air Quality and Health, Queensland University of Technology, Brisbane, Qld, Australia
| | - L Morawska
- International Laboratory for Air Quality and Health, Queensland University of Technology, Brisbane, Qld, Australia
| | - G Buonanno
- Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, FR, Italy
- International Laboratory for Air Quality and Health, Queensland University of Technology, Brisbane, Qld, Australia
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44
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COVID-19 Impact on Operation and Energy Consumption of Heating, Ventilation and Air-Conditioning (HVAC) Systems. ADVANCES IN APPLIED ENERGY 2021; 3. [PMCID: PMC8166037 DOI: 10.1016/j.adapen.2021.100040] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Heating, ventilation and air-conditioning (HVAC) system is favourable for regulating indoor temperature, relative humidity, airflow pattern and air quality. However, HVAC systems may turn out to be the culprit of microbial contamination in enclosed spaces and deteriorate the environment due to inappropriate design and operation. In the context of COVID-19, significant transformations and new requirements are occurring in HVAC systems. Recently, several updated operational guidelines for HVAC systems have been issued by various institutions to control the airborne transmission and mitigate infection risks in enclosed environments. Challenges and innovations emerge in response to operational variations of HVAC systems. To efficiently prevent the spread of the pandemic and reduce infection risks, it is essential to have an overall understanding of impacts caused by COVID-19 on HVAC systems. Therefore, the objectives of this article are to: (a) provide a comprehensive review of the airborne transmission characteristics of SARS-CoV-2 in enclosed spaces and a theoretical basis for HVAC operation guideline revision; (b) investigate HVAC-related guidelines to clarify the operational variations of HVAC systems during the pandemic; (c) analyse how operational variations of HVAC systems affect energy consumption; and (d) identify the innovations and research trends concerning future HVAC systems. Furthermore, this paper compares the energy consumption of HVAC system operation during the normal times versus pandemic period, based on a case study in China, providing a reference for other countries around the world. Results of this paper offer comprehensive insights into how to keep indoor environments safe while maintaining energy-efficient operation of HVAC systems.
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Key Words
- energy impacts of hvac systems
- covid-19 pandemic
- airborne transmission
- hvac operation guidelines
- challenges and innovations
- ahu, air handing unit
- asc, architectural society of china
- ashrae, american society of heating refrigerating and air-conditioning engineers
- car, chinese association of refrigeration
- cciaq, canadian committee on indoor air quality
- cop, coefficient of performance
- dcv, demand-controlled ventilation
- ecdc, european centre for disease prevention and control
- eeaf, electrostatic enhanced air filter
- eepf, electrostatic enhanced pleated air filters
- hepa, high efficiency particulate air
- hphe, heat pipe heat exchanger
- epa, environmental protection agency
- hvac, heating, ventilation and air-conditioning
- ishrae, indian society of heating refrigerating and air conditioning engineers
- merv, minimum efficiency reporting value
- mohurd, ministry of housing and urban-rural development of the people's republic of china
- nhc, national health commission of china
- pho, public health ontario
- rehva, federation of european heating ventilation and air conditioning associations
- sac, standardization administration of the people's republic of china
- sbs, sick building syndrome
- shase, society of heating air-conditioning and sanitary engineers in japan
- uv, ultraviolet
- uvgi, ultraviolet germicidal irradiation
- who, world health organization
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45
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Rowe BR, Canosa A, Drouffe JM, Mitchell JBA. Simple quantitative assessment of the outdoor versus indoor airborne transmission of viruses and COVID-19. ENVIRONMENTAL RESEARCH 2021; 198:111189. [PMID: 33872644 PMCID: PMC8051020 DOI: 10.1016/j.envres.2021.111189] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 04/06/2021] [Accepted: 04/12/2021] [Indexed: 05/15/2023]
Abstract
In this paper we develop a simple model of the inhaled flow rate of aerosol particles of respiratory origin i.e. that have been exhaled by other people. A connection is made between the exposure dose and the probability of developing an airborne disease. This allows a simple assessment of the outdoor versus indoor risk of contamination to be made in a variety of meteorological situations. It is shown quantitatively that for most cases, the outdoor risk is orders of magnitude less than the indoor risk and that it can become comparable only for extremely specific meteorological and topographical situations. It sheds light on various observations of COVID-19 spreading in mountain valleys with temperature inversions while at the same time other areas are much less impacted.
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Affiliation(s)
- B R Rowe
- Rowe Consulting, 22 Chemin des Moines, 22750, Saint Jacut de La Mer, France.
| | - A Canosa
- CNRS, IPR (Institut de Physique de Rennes)-UMR 6251, Université de Rennes, 35000, Rennes, France
| | - J M Drouffe
- 31B Chemin Du Couvent, 91190, Gif-sur-Yvette, France
| | - J B A Mitchell
- MERL-Consulting SAS, 21 Rue Sergent Guihard, 35000, Rennes, France
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46
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Shah Y, Kurelek JW, Peterson SD, Yarusevych S. Experimental investigation of indoor aerosol dispersion and accumulation in the context of COVID-19: Effects of masks and ventilation. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2021; 33:073315. [PMID: 34335009 PMCID: PMC8320385 DOI: 10.1063/5.0057100] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Accepted: 07/02/2021] [Indexed: 05/04/2023]
Abstract
The ongoing COVID-19 pandemic has highlighted the importance of aerosol dispersion in disease transmission in indoor environments. The present study experimentally investigates the dispersion and build-up of an exhaled aerosol modeled with polydisperse microscopic particles (approximately 1 μm mean diameter) by a seated manikin in a relatively large indoor environment. The aims are to offer quantitative insight into the effect of common face masks and ventilation/air purification, and to provide relevant experimental metrics for modeling and risk assessment. Measurements demonstrate that all tested masks provide protection in the immediate vicinity of the host primarily through the redirection and reduction of expiratory momentum. However, leakages are observed to result in notable decreases in mask efficiency relative to the ideal filtration efficiency of the mask material, even in the case of high-efficiency masks, such as the R95 or KN95. Tests conducted in the far field ( 2 m distance from the subject) capture significant aerosol build-up in the indoor space over a long duration ( 10 h ). A quantitative measure of apparent exhalation filtration efficiency is provided based on experimental data assimilation to a simplified model. The results demonstrate that the apparent exhalation filtration efficiency is significantly lower than the ideal filtration efficiency of the mask material. Nevertheless, high-efficiency masks, such as the KN95, still offer substantially higher apparent filtration efficiencies (60% and 46% for R95 and KN95 masks, respectively) than the more commonly used cloth (10%) and surgical masks (12%), and therefore are still the recommended choice in mitigating airborne disease transmission indoors. The results also suggest that, while higher ventilation capacities are required to fully mitigate aerosol build-up, even relatively low air-change rates ( 2 h - 1 ) lead to lower aerosol build-up compared to the best performing mask in an unventilated space.
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Affiliation(s)
- Yash Shah
- Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - John W. Kurelek
- Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Sean D. Peterson
- Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Serhiy Yarusevych
- Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
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47
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Mirikar D, Palanivel S, Arumuru V. Droplet fate, efficacy of face mask, and transmission of virus-laden droplets inside a conference room. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2021; 33:065108. [PMID: 34248325 PMCID: PMC8232678 DOI: 10.1063/5.0054110] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 05/13/2021] [Indexed: 05/16/2023]
Abstract
The second and third waves of coronavirus disease-2019 (COVID-19) pandemic have hit the world. Even after more than a year, the economy is yet to return to a semblance of normality. The conference/meeting room is one of the critical sections of offices that might be difficult not to use. This study analyzes the distribution of the virus-laden droplets expelled by coughing inside a conference room, the effect of ventilation rates, and their positioning. The efficacy of masks is studied to get quantitative information regarding the residence time of the droplets. The effects of evaporation, turbulent dispersion, and external forces have been considered for calculating the droplets' trajectories. We have analyzed six cases, of which two are with masks. Change in the ventilation rate from four air changes per hour (ACH) to eight resulted in a 9 % increment in the number of droplets entrained in the outlet vent, while their average residence time was reduced by ∼ 8 s . The shift in the vents' location has significantly altered droplets' distribution inside a conference room. It results in ∼ 1.5 % of the injected droplets reaching persons sitting across the table, and a similar indoor environment is not recommended. Wearing a mask in the case of eight ACH has presented the best scenario out of the six cases, with a 6.5 % improvement in the number of droplets entrained in the outlet vent and a 9 s decrease in their average residence time compared to the case without a mask. No droplets have reached persons sitting across the table when the infected person is wearing the mask, which follows that a social distancing of 6 ft with a mask is adequate in indoor environments.
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Affiliation(s)
- Dnyanesh Mirikar
- Applied Fluids Group, School of Mechanical Sciences, Indian Institute of Technology Bhubaneswar, Bhubaneswar 752050, India
| | - Silambarasan Palanivel
- Applied Fluids Group, School of Mechanical Sciences, Indian Institute of Technology Bhubaneswar, Bhubaneswar 752050, India
| | - Venugopal Arumuru
- Applied Fluids Group, School of Mechanical Sciences, Indian Institute of Technology Bhubaneswar, Bhubaneswar 752050, India
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48
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Rezaei M, Netz RR. Airborne virus transmission via respiratory droplets: Effects of droplet evaporation and sedimentation. Curr Opin Colloid Interface Sci 2021; 55:101471. [PMID: 34093064 PMCID: PMC8164513 DOI: 10.1016/j.cocis.2021.101471] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Airborne transmission is considered as an important route for the spread of infectious diseases, such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and is primarily determined by the droplet sedimentation time, that is, the time droplets spend in air before reaching the ground. Evaporation increases the sedimentation time by reducing the droplet mass. In fact, small droplets can, depending on their solute content, almost completely evaporate during their descent to the ground and remain airborne as so-called droplet nuclei for a long time. Considering that viruses possibly remain infectious in aerosols for hours, droplet nuclei formation can substantially increase the infectious viral air load. Accordingly, the physical-chemical factors that control droplet evaporation and sedimentation times and play important roles in determining the infection risk from airborne respiratory droplets are reviewed in this article.
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Affiliation(s)
- Majid Rezaei
- Fachbereich Physik, Freie Universität Berlin, Berlin, 14195, Germany
| | - Roland R Netz
- Fachbereich Physik, Freie Universität Berlin, Berlin, 14195, Germany
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49
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Schibuola L, Tambani C. Performance comparison of heat recovery systems to reduce viral contagion in indoor environments. APPLIED THERMAL ENGINEERING 2021; 190:116843. [PMID: 34720655 PMCID: PMC8546945 DOI: 10.1016/j.applthermaleng.2021.116843] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2021] [Revised: 02/25/2021] [Accepted: 03/07/2021] [Indexed: 05/07/2023]
Abstract
Strong ventilation increments are currently suggested for containing the airborne diffusion of COVID-19 in indoor environments. However, it can involve an unacceptable growing of energy consumption. Therefore, maximum care must be addressed to improve efficiency of ventilation heat recovery (VHR). For this purpose, this paper investigates the opportunity of a technical solution. Consisting in adding downstream of the most diffuse heat recuperator, a heat pump using exhaust air as a cold source. An autonomous high efficiency air handling unit (HEAHU) was modelled for a school application. By simulation a performance comparison was carried on with two alternative systems based only on an exhaust air heat pump (EAHP) or on a heat recuperator for different weather conditions. Results indicated that the milder climate strongly penalizes heat recuperator and this fact deeply influences the conclusions. HEAHU saving compared to energy consumption of only heat recuperator is between 31% and 46%. For EAHP this saving varies from 2.5% to 48%. Only with a milder climate, EAHP presents a lightly greater saving than HEAHU. Heat pump technology looks to be very performing to foster the efficiency of VHR, especially in presence of high ventilation rates.
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Affiliation(s)
- Luigi Schibuola
- University IUAV of Venice, Dorsoduro 2206, 30123 Venice, Italy
| | - Chiara Tambani
- University IUAV of Venice, Dorsoduro 2206, 30123 Venice, Italy
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50
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Zhang S, Lin Z. Dilution-based evaluation of airborne infection risk - Thorough expansion of Wells-Riley model. BUILDING AND ENVIRONMENT 2021; 194:107674. [PMID: 33583999 DOI: 10.1101/2020.10.03.20206391] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 01/16/2021] [Accepted: 02/03/2021] [Indexed: 05/25/2023]
Abstract
Evaluation of airborne infection risk with spatial and temporal resolutions is indispensable for the design of proper interventions fighting infectious respiratory diseases (e.g., COVID-19), because the distribution of aerosol contagions is both spatially and temporally non-uniform. However, the well-recognized Wells-Riley model and modified Wells-Riley model (i.e., the rebreathed-fraction model) are limited to the well-mixed condition and unable to evaluate airborne infection risk spatially and temporally, which could result in overestimation or underestimation of airborne infection risk. This study proposes a dilution-based evaluation method for airborne infection risk. The method proposed is benchmarked by the Wells-Riley model and modified Wells-Riley model, which indicates that the method proposed is a thorough expansion of the Wells-Riley model for evaluation of airborne infection risk with both spatial and temporal resolutions. Experiments in a mock hospital ward also demonstrate that the method proposed effectively evaluates the airborne infection risk both spatially and temporally. The proposed method is convenient to implement for the development of healthy built environments.
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Affiliation(s)
- Sheng Zhang
- Division of Building Science and Technology, City University of Hong Kong, Hong Kong, China
| | - Zhang Lin
- Division of Building Science and Technology, City University of Hong Kong, Hong Kong, China
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