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Tsang TW, Mui KW, Wong LT, Law KY, Shek KW. A Novel IoT-Enabled Wireless Sensor Grid for Spatial and Temporal Evaluation of Tracer Gas Dispersion. SENSORS (BASEL, SWITZERLAND) 2023; 23:3920. [PMID: 37112265 PMCID: PMC10145748 DOI: 10.3390/s23083920] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 04/07/2023] [Accepted: 04/11/2023] [Indexed: 06/19/2023]
Abstract
Current IoT applications in indoor air focus mainly on general monitoring. This study proposed a novel IoT application to evaluate airflow patterns and ventilation performance using tracer gas. The tracer gas is a surrogate for small-size particles and bioaerosols and is used in dispersion and ventilation studies. Prevalent commercial tracer-gas-measuring instruments, although highly accurate, are relatively expensive, have a long sampling cycle, and are limited in the number of sampling points. To enhance the spatial and temporal understanding of tracer gas dispersion under the influence of ventilation, a novel application of an IoT-enabled, wireless R134a sensing network using commercially available small sensors was proposed. The system has a detection range of 5-100 ppm and a sampling cycle of 10 s. Using Wi-Fi communication, the measurement data are transmitted to and stored in a cloud database for remote, real-time analysis. The novel system provides a quick response, detailed spatial and temporal profiles of the tracer gas level, and a comparable air change rate analysis. With multiple units deployed as a wireless sensing network, the system can be applied as an affordable alternative to traditional tracer gas systems to identify the dispersion pathway of the tracer gas and the general airflow direction.
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Affiliation(s)
- Tsz-Wun Tsang
- Department of Building Environment and Energy Engineering, The Hong Kong Polytechnic University, Hong Kong, China
| | - Kwok-Wai Mui
- Department of Building Environment and Energy Engineering, The Hong Kong Polytechnic University, Hong Kong, China
| | - Ling-Tim Wong
- Department of Building Environment and Energy Engineering, The Hong Kong Polytechnic University, Hong Kong, China
| | - Kwok-Yung Law
- Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hong Kong, China
| | - Ka-Wing Shek
- Department of Building Environment and Energy Engineering, The Hong Kong Polytechnic University, Hong Kong, China
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Dai Y, Xu D, Wang H, Zhang F. CFD Simulations of Ventilation and Interunit Dispersion in Dormitory Complex: A Case Study of Epidemic Outbreak in Shanghai. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2023; 20:4603. [PMID: 36901611 PMCID: PMC10002394 DOI: 10.3390/ijerph20054603] [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: 01/31/2023] [Revised: 02/28/2023] [Accepted: 03/02/2023] [Indexed: 06/18/2023]
Abstract
Since the beginning of March 2022, a new round of COVID-19 outbreaks in Shanghai has led to a sharp increase in the number of infected people. It is important to identify possible pollutant transmission routes and predict potential infection risks for infectious diseases. Therefore, this study investigated the cross-diffusion of pollutants caused by natural ventilation, including external windows and indoor ventilation windows, under three wind directions in a densely populated building environment with the CFD method. In this study, CFD building models were developed based on an actual dormitory complex and surrounding buildings under realistic wind conditions to reproduce the airflow fields and transmission paths of pollutants. This paper adopted the Wells-Riley model to assess the risk of cross-infection. The biggest risk of infection was when a source room was located on the windward side, and the risk of infection in other rooms on the same side as the source room was large in the windward direction. When pollutants were released from room 8, north wind resulted in the highest concentration of pollutants in room 28, reaching 37.8%. This paper summarizes the transmission risks related to the indoor and outdoor environments of compact buildings.
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3
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Zheng J, Tao Q, Chen Y. Airborne infection risk of inter-unit dispersion through semi-shaded openings: A case study of a multi-storey building with external louvers. BUILDING AND ENVIRONMENT 2022; 225:109586. [PMID: 36105610 PMCID: PMC9461617 DOI: 10.1016/j.buildenv.2022.109586] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 08/17/2022] [Accepted: 09/05/2022] [Indexed: 06/15/2023]
Abstract
Building design for natural ventilation and indoor air quality have become increasingly important during the past decades. Investigating airflow routes of airborne transmission and evaluating the potential infection risk in the multi-storey building is helpful to the reduction of airborne transmission. Therefore, this study applies computational fluid dynamics simulations to investigate the inter-unit dispersion pattern of gaseous pollutant between different units through semi-shaded openings. The airflow exchange and pollutant dispersion in a multi-storey building is driven by wind-induced natural ventilation. External shading louvers, which are widely used in building facades to reduce heat gain from solar radiation, are chosen to establish the semi-shaded environment. Experimental validation is performed to make sure the accuracy of numerical settings in airflow investigation of semi-shaded openings. The airflow characteristics around semi-shaded openings is analyzed in the numerical simulations. The re-entry ratio of tracer gas and the airborne infection risk of COVID-19 is investigated in the cases with different louvers' locations and source units. The results show that the airflow is commonly slower in the semi-shaded space between louvers and openings. But the ventilation rate is not always consistent with the airflow speed because of the diversion effect from louver slats. The inter-unit infectious risk in the worst unit rises from 7.82% to 26.17% for windward shading, while it rises from 7.89% to 22.52% for leeward shading. These results are helpful to the further understanding of inter-unit transmission of infectious respiratory aerosols through external openings with complex structures.
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Affiliation(s)
- Jianwen Zheng
- College of Mechanical and Energy Engineering, Jimei University, Xiamen, 361021, China
| | - Qiuhua Tao
- College of Mechanical and Energy Engineering, Jimei University, Xiamen, 361021, China
- Fujian Province Key Laboratory of Energy Cleaning Utilization and Development, Xiamen, 361021, China
| | - Yangui Chen
- College of Mechanical and Energy Engineering, Jimei University, Xiamen, 361021, China
- Fujian Province Key Laboratory of Energy Cleaning Utilization and Development, Xiamen, 361021, China
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4
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Cheng P, Chen W, Xiao S, Xue F, Wang Q, Chan PW, You R, Lin Z, Niu J, Li Y. Probable cross-corridor transmission of SARS-CoV-2 due to cross airflows and its control. BUILDING AND ENVIRONMENT 2022; 218:109137. [PMID: 35502296 PMCID: PMC9045881 DOI: 10.1016/j.buildenv.2022.109137] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 03/12/2022] [Accepted: 04/20/2022] [Indexed: 06/01/2023]
Abstract
A COVID-19 outbreak occurred in May 2020 in a public housing building in Hong Kong - Luk Chuen House, located in Lek Yuen Estate. The horizontal cluster linked to the index case' flat (flat 812) remains to be explained. Computational fluid dynamics simulations were conducted to obtain the wind-pressure coefficients of each external opening on the eighth floor of the building. The data were then used in a multi-zone airflow model to estimate the airflow rate and aerosol concentration in the flats and corridors on that floor. Apart from flat 812 and corridors, the virus-laden aerosol concentrations in flats 811, 813, 815, 817 and 819 (opposite to flat 812, across the corridor) were the highest on the eighth floor. When the doors of flats 813 and 817 were opened by 20%, the hourly-averaged aerosol concentrations in these two flats were at least four times as high as those in flats 811, 815 and 819 during the index case's home hours or the suspected exposure period of secondary cases. Thus, the flats across the corridor that were immediately downstream from flat 812 were at the highest exposure risk under a prevailing easterly wind, especially when their doors or windows that connected to the corridor were open. Given that the floorplan and dimension of Luk Chuen House are similar to those of many hotels, our findings provide a probable explanation for COVID-19 outbreaks in quarantine hotels. Positive pressure and sufficient ventilation in the corridor would help to minimise such cross-corridor infections.
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Affiliation(s)
- Pan Cheng
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong SAR, China
| | - Wenzhao Chen
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong SAR, China
| | - Shenglan Xiao
- School of Public Health (Shenzhen), Sun Yat-sen University, Shenzhen, China
| | - Fan Xue
- Department of Real Estate and Construction, The University of Hong Kong, Hong Kong SAR, China
| | - Qun Wang
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong SAR, China
| | - Pak Wai Chan
- Hong Kong Observatory, Kowloon, Hong Kong SAR, China
| | - Ruoyu You
- Department of Building Environment and Energy Engineering, The Hong Kong Polytechnic University, Hong Kong SAR, China
| | - Zhang Lin
- Division of Building Science and Technology, City University of Hong Kong, Hong Kong SAR, China
| | - Jianlei Niu
- Department of Building Environment and Energy Engineering, The Hong Kong Polytechnic University, Hong Kong SAR, China
| | - Yuguo Li
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong SAR, China
- School of Public Health, The University of Hong Kong, Hong Kong SAR, China
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5
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Wang Q, Lin Z, Niu J, Choi GKY, Fung JCH, Lau AKH, Louie P, Leung KKM, Huang J, Cheng P, Zhao P, Chen W, Zhang S, Fu L, Chan PW, Wong AH, Tse H, Wong SCY, Lai RWM, Hui DS, Yuen KY, Lung DC, Li Y. Spread of SARS-CoV-2 aerosols via two connected drainage stacks in a high-rise housing outbreak of COVID-19. JOURNAL OF HAZARDOUS MATERIALS 2022; 430:128475. [PMID: 35183827 PMCID: PMC8832857 DOI: 10.1016/j.jhazmat.2022.128475] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Revised: 02/08/2022] [Accepted: 02/09/2022] [Indexed: 05/07/2023]
Abstract
Vertical transmission of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) along a vertical column of flats has been documented in several outbreaks of coronavirus disease 2019 (COVID-19) in Guangdong and Hong Kong. We describe an outbreak in Luk Chuen House, involving two vertical columns of flats associated with an unusually connected two-stack drainage system, in which nine individuals from seven households were infected. The index case resided in Flat 812 (8th floor, Unit 12), two flats (813, 817) on its opposite side reported one case each (i.e., a horizontal sub-cluster). All other flats with infected residents were vertically associated, forming a vertical sub-cluster. We injected tracer gas (SF6) into drainage stacks via toilet or balcony of Flat 812, monitored gas concentrations in roof vent, toilet, façade, and living room in four of the seven flats with infected residents and four flats with no infected residents. The measured gas concentration distributions agreed with the observed distribution of affected flats. Aerosols leaking into drainage stacks may generate the vertical sub-cluster, whereas airflow across the corridor probably caused the horizontal sub-cluster. Sequencing and phylogenetic analyses also revealed a common point-source. The findings provided additional evidence of probable roles of drainage systems in SARS-CoV-2 transmission.
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Affiliation(s)
- Qun Wang
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China
| | - Zhang Lin
- Division of Building Science and Technology, City University of Hong Kong, Hong Kong, China
| | - Jianlei Niu
- Department of Building Environment and Energy Engineering, The Hong Kong Polytechnic University, Hong Kong, China
| | | | - Jimmy C H Fung
- Division of Environment & Sustainability, Hong Kong University of Science and Technology, Hong Kong, China
| | - Alexis K H Lau
- Division of Environment & Sustainability, Hong Kong University of Science and Technology, Hong Kong, China
| | - Peter Louie
- Environmental Protection Department, Hong Kong SAR Government, Hong Kong, China
| | - Kenneth K M Leung
- Environmental Protection Department, Hong Kong SAR Government, Hong Kong, China
| | - Jianxiang Huang
- Department of Urban Planning and Design, Faculty of Architecture, The University of Hong Kong, Hong Kong, China
| | - Pan Cheng
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China
| | - Pengcheng Zhao
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China
| | - Wenzhao Chen
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China
| | - Sheng Zhang
- Division of Building Science and Technology, City University of Hong Kong, Hong Kong, China
| | - Liye Fu
- Department of Building Environment and Energy Engineering, The Hong Kong Polytechnic University, Hong Kong, China
| | - P W Chan
- Hong Kong Observatory, Kowloon, Hong Kong, China
| | - Ann Han Wong
- Department of Microbiology, Prince of Wales Hospital, Hong Kong, China
| | - Herman Tse
- Department of Pathology, Hong Kong Children's Hospital, Hong Kong, China
| | | | | | - David Sc Hui
- Department of Medicine and Therapeutics, Chinese University of Hong Kong, Hong Kong, China
| | - Kwok-Yung Yuen
- Department of Microbiology, The University of Hong Kong, Hong Kong, China
| | - David Christopher Lung
- Department of Pathology, Hong Kong Children's Hospital, Hong Kong, China; Department of Pathology, Queen Elizabeth Hospital, Hong Kong, China.
| | - Yuguo Li
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China.
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Study on ventilation rates and assessment of infection risks of COVID-19 in an outpatient building. JOURNAL OF BUILDING ENGINEERING 2021; 42:103090. [PMCID: PMC8352663 DOI: 10.1016/j.jobe.2021.103090] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Revised: 08/02/2021] [Accepted: 08/05/2021] [Indexed: 05/24/2023]
Abstract
A modified Wells-Riley model combining the airborne route and close contact route was proposed to predict the infection risks of coronavirus disease 2019 (COVID-19) in main functional spaces of an outpatient building in Shenzhen, China. The personnel densities and ventilation rates in the 20 waiting rooms, outpatient hall and hospital street were on-site measured. The average fresh air volume per person and occupant area per person in the 20 waiting rooms were 77.6 m3/h and 6.47 m2/per, satisfied with the Chinese standard. The average waiting time of the occupants was 0.69 h. Thus, assuming the proportion of infected people in the outpatient building was 2%, the daily average infection probabilities of COVID-19 in the 20 waiting rooms were 0.19–1.88% with a reasonable setting of the quanta produced by an infector (q = 45 quanta/h) and the effective exposure dose of pathogen per unit close contact time (β = 0.05 h−1). The design of the semi-closed hospital street with a height of 24 m improved its natural ventilation with a fresh air volume per person of 70–185 m3/h and further dilute the viral aerosol and decreased the infection risk to a negligible level (i.e., below 0.04% with an infector proportion of 2%). The assessment method provides real-time prediction of indoor infection risk and good assist in spread control of COVID-19.
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7
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Tung CW, Mak CM, Niu JL, Hung K, Wu Y, Tung N, Wong HM. Enlightenment of re-entry airflow: The path of the airflow and the airborne pollutants transmission in buildings. BUILDING AND ENVIRONMENT 2021; 195:107760. [PMID: 34840404 PMCID: PMC8609235 DOI: 10.1016/j.buildenv.2021.107760] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2020] [Revised: 02/05/2021] [Accepted: 02/25/2021] [Indexed: 05/24/2023]
Abstract
Viable aerosols in the airflow may increase the risk of occupants contracting diseases. Natural ventilation is common in buildings and is accompanied by re-entry airflow during the ventilation process. If the re-entry airflow contains toxic or infectious species, it may cause potential harm to residents. One of the Covid-19 outbreaks occurred in a public residential building at Luk Chuen House (LC-House) in Hong Kong. It is highly suspected that the outbreak of the disease is related to the re-entry airflow. The study attempts to explain and discuss possible causes of the outbreak. In order to understand the impact of airflow on the outbreak, a public residential building similar to LC-House was used in the study. Two measurements M - I and M - II with the same settings were conducted for a sampling unit in the corridor under low and strong wind conditions respectively. The sampling unit and the tracer gas carbon dioxide (CO2) were used to simulate the index unit and infectious contaminated airflow respectively. The CO2 concentrations of the unit and corridor were measured simultaneously. Two models of Traditional Single-zone model (TSZ-model) and New Dual-zone model (NDZ-model) were used in the analysis. By comparing the ACH values obtained from the two models, it is indicated that the re-entry airflow of the unit is related to the corridor wind speeds and this provides a reasonable explanation for the outbreak in LC-House, and believes that the results can help understand the recent frequent cluster outbreaks in other residential buildings.
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Affiliation(s)
- C W Tung
- Department of Building Services Engineering, The Hong Kong Polytechnic University, Hong Kong, China
| | - C M Mak
- Department of Building Services Engineering, The Hong Kong Polytechnic University, Hong Kong, China
| | - J L Niu
- Department of Building Services Engineering, The Hong Kong Polytechnic University, Hong Kong, China
| | - K Hung
- Department of Building Services Engineering, The Hong Kong Polytechnic University, Hong Kong, China
| | - Yan Wu
- School of Mechanical Engineering, Tongji University, China
| | - Nam Tung
- Department of Building Services Engineering, The Hong Kong Polytechnic University, Hong Kong, China
| | - H M Wong
- Faculty of Dentistry, The University of Hong Kong, Pok Fu Lam, Hong Kong Island, Hong Kong, China
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8
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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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9
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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 PMCID: PMC7871780 DOI: 10.1016/j.buildenv.2021.107674] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [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: 05/05/2023]
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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10
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Reichman R, Dubowski Y. Gaseous pollutant transport from an underground parking garage in a Mediterranean multi-story building-Effect of temporal resolution under varying weather conditions. BUILDING SIMULATION 2021; 14:1511-1523. [PMID: 33649710 PMCID: PMC7905197 DOI: 10.1007/s12273-020-0757-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 11/29/2020] [Accepted: 12/10/2020] [Indexed: 06/12/2023]
Abstract
Indoor air dynamics and quality in high density residential buildings can be complex as it is affected by both building parameters, pollution sources, and outdoor meteorological conditions. The present study used CONTAM simulations to investigate the intra-building transport and concentration of an inert pollutant continuously emitted from an underground garage of a 15-floor building under moderate Mediterranean weather. The effects of outdoor meteorological conditions (air temperature, wind speed and direction) on indoor distribution of the emitted pollutant was tested under constant conditions. The importance of using actual transient meteorological data and the impact of their temporal resolution on calculated concentrations and exposure levels were also investigated. Vertical profiles of air exchange rate (AER) and CO concentration were shown to be sensitive to indoor-outdoor temperature difference, which controls the extent of the stack effect and its importance relative to wind effect. Even under constant conditions, transient mode simulations revealed that the time needed for pollutant distribution to reach steady state can be quite long (>24h in some cases). The temporal resolution (1h vs. 8h) of the meteorological data input was also found to impact calculated exposure levels, in an extent that varied with time, meteorological conditions and apartment position.
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Affiliation(s)
- Rivka Reichman
- Faculty of Civil and Environmental Engineering, Technion — Israel Institute of Technology, Haifa, 32000 Israel
| | - Yael Dubowski
- Faculty of Civil and Environmental Engineering, Technion — Israel Institute of Technology, Haifa, 32000 Israel
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11
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Azimi P, Keshavarz Z, Cedeno Laurent JG, Allen JG. Estimating the nationwide transmission risk of measles in US schools and impacts of vaccination and supplemental infection control strategies. BMC Infect Dis 2020; 20:497. [PMID: 32652940 PMCID: PMC7351650 DOI: 10.1186/s12879-020-05200-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Accepted: 06/25/2020] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND The spread of airborne infectious diseases such as measles is a critical public health concern. The U.S. was certified measles-free in 2000, but the number of measles cases has increased in recent years breaking the record of the nationwide annual number of cases since 1992. Although the characteristics of schools have made them one of the most vulnerable environments during infection outbreaks, the transmission risk of measles among students is not completely understood. We aimed to evaluate how three factors influence measles transmission in schools: personal (vaccination), social (compartmentalizing), and building systems (ventilation, purification, and filtration). METHODS We used a combination of a newly developed multi-zone transient Wells-Riley approach, a nationwide representative School Building Archetype (SBA) model, and a Monte-Carlo simulation to estimate measles risk among U.S. students. We compared our risk results with the range of reported transmission rates of measles in school outbreaks to validate the risk model. We also investigated the effectiveness of vaccination and ten supplemental infection control scenarios for reducing the risk of measles transmission among students. RESULTS Our best nationwide estimate of measles transmission risk in U.S. schools were 3.5 and 32% among all (both unvaccinated and immunized) and unvaccinated students, respectively. The results showed the transmission risk of measles among unvaccinated students is > 70 times higher than properly immunized ones. We also demonstrated that the transmission risk of measles in primary schools (assuming teacher self-contained classrooms) is less than secondary schools (assuming departmentalized systems). For building-level interventions, schools with ductless-with-air-filter and ductless-without-air-filter systems have the lowest and highest transmission risks of measles, respectively. Finally, our simulation showed that infection control strategies could cut the average number of infected cases among all students in half when a combination of advanced air filtration, ventilation, and purification was adopted in the modeled schools. CONCLUSIONS Our results highlight the primary importance of vaccination for reducing the risk of measles transmission among students. Yet, additional and significant risk reduction can be achieved through compartmentalizing students and enhancing building ventilation and filtration systems.
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Affiliation(s)
- Parham Azimi
- Department of Environmental Health, Harvard T. H. Chan School of Public Health, Boston, USA.
| | - Zahra Keshavarz
- Department of Environmental Health, Harvard T. H. Chan School of Public Health, Boston, USA
| | | | - Joseph G Allen
- Department of Environmental Health, Harvard T. H. Chan School of Public Health, Boston, USA
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12
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Wang J, Huo Q, Zhang T, Wang S, Battaglia F. Numerical investigation of gaseous pollutant cross-transmission for single-sided natural ventilation driven by buoyancy and wind. BUILDING AND ENVIRONMENT 2020; 172:106705. [PMID: 32287994 PMCID: PMC7116971 DOI: 10.1016/j.buildenv.2020.106705] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Revised: 01/28/2020] [Accepted: 01/29/2020] [Indexed: 05/13/2023]
Abstract
Single-sided natural ventilation was numerically investigated to determine the impact of buoyancy and wind on the cross-transmission of pollution by considering six window types commonly found in multistory buildings. The goal of this study was to predict the gaseous pollutant transmission using computational fluid dynamics based on the Reynolds-averaged Navier-Stokes equations and baseline k-ω turbulence equations. The results indicated that ventilation rates generally increased with increasing wind speeds if the effects of buoyancy and wind were not suppressed; however, the re-entry ratio representing the proportion of expelled air re-entering other floors and the corresponding risk of infection decreased. If the source of the virus was on a central floor, the risk of infection was the highest on the floors closest to the source. Different window types were also considered for determining their effectiveness in controlling cross-transmission and infection risk, depending on the source location and driving force (e.g., buoyancy and wind).
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Affiliation(s)
- Jihong Wang
- School of Civil Engineering, Dalian University of Technology, 2 Linggong Road, Dalian, 116024, China
| | - Qiannan Huo
- School of Civil Engineering, Dalian University of Technology, 2 Linggong Road, Dalian, 116024, China
| | - Tengfei Zhang
- School of Civil Engineering, Dalian University of Technology, 2 Linggong Road, Dalian, 116024, China
| | - Shugang Wang
- School of Civil Engineering, Dalian University of Technology, 2 Linggong Road, Dalian, 116024, China
| | - Francine Battaglia
- Department of Mechanical & Aerospace Engineering, University at Buffalo, 339 Jarvis Hall, Buffalo, NY, 14260, USA
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13
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Wang J, Huo Q, Zhang T, Wang S, Battaglia F. Numerical investigation of gaseous pollutant cross-transmission for single-sided natural ventilation driven by buoyancy and wind. BUILDING AND ENVIRONMENT 2020. [PMID: 32287994 DOI: 10.1016/j.enbuild.2018.03.015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Single-sided natural ventilation was numerically investigated to determine the impact of buoyancy and wind on the cross-transmission of pollution by considering six window types commonly found in multistory buildings. The goal of this study was to predict the gaseous pollutant transmission using computational fluid dynamics based on the Reynolds-averaged Navier-Stokes equations and baseline k-ω turbulence equations. The results indicated that ventilation rates generally increased with increasing wind speeds if the effects of buoyancy and wind were not suppressed; however, the re-entry ratio representing the proportion of expelled air re-entering other floors and the corresponding risk of infection decreased. If the source of the virus was on a central floor, the risk of infection was the highest on the floors closest to the source. Different window types were also considered for determining their effectiveness in controlling cross-transmission and infection risk, depending on the source location and driving force (e.g., buoyancy and wind).
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Affiliation(s)
- Jihong Wang
- School of Civil Engineering, Dalian University of Technology, 2 Linggong Road, Dalian, 116024, China
| | - Qiannan Huo
- School of Civil Engineering, Dalian University of Technology, 2 Linggong Road, Dalian, 116024, China
| | - Tengfei Zhang
- School of Civil Engineering, Dalian University of Technology, 2 Linggong Road, Dalian, 116024, China
| | - Shugang Wang
- School of Civil Engineering, Dalian University of Technology, 2 Linggong Road, Dalian, 116024, China
| | - Francine Battaglia
- Department of Mechanical & Aerospace Engineering, University at Buffalo, 339 Jarvis Hall, Buffalo, NY, 14260, USA
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14
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Dai Y, Mak CM, Zhang Y, Cui D, Hang J. Investigation of interunit dispersion in 2D street canyons: A scaled outdoor experiment. BUILDING AND ENVIRONMENT 2020; 171:106673. [PMID: 32287993 DOI: 10.1016/j.buildenv.2020.106653] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2019] [Revised: 01/04/2020] [Accepted: 01/11/2020] [Indexed: 05/22/2023]
Abstract
Interunit dispersion problems have been studied previously mainly through on-site measurements, wind tunnel tests, and CFD simulations. In this study, a scaled outdoor experiment was conducted to examine the interunit dispersion characteristics in consecutive two-dimensional street canyons. Tracer gas ( C O 2 ) was continuously released to simulate the pollutant dispersion routes between the rooms in street canyons. The wind velocity, wind direction, air temperature, and tracer gas concentrations were monitored simultaneously. Two important parameters, the air exchange rate and reentry ratio, were analyzed to reveal the ventilation performance and interunit dispersion of the rooms in the street canyons. Based on the real-time weather conditions, it was found that the ventilation performance of the source room varied according to the room location. The air exchange rate distribution of the leeward-side room was more stable than that of the windward side. The tracer gas was mainly transported in the vortex direction inside the street canyon, and the highest reentry ratio was observed at the room nearest to the source room along the transportation route. In addition, under real weather conditions, the rooms in the street canyon have a high probability of experiencing a high reentry ratio based on the maximum reentry ratio of each room. This study provides authentic airflow and pollutant dispersion information in the street canyons in an urban environment. The dataset of this experiment can be used to validate further numerical simulations.
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Affiliation(s)
- Yuwei Dai
- Department of Building Services Engineering, The Hong Kong Polytechnic University, Hong Kong, PR China
| | - Cheuk Ming Mak
- Department of Building Services Engineering, The Hong Kong Polytechnic University, Hong Kong, PR China
| | - Yong Zhang
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, 510275, PR China
| | - Dongjin Cui
- School of Architecture & Urban Planning, Shenzhen University, Shenzhen, 518060, PR China
| | - Jian Hang
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, 510275, PR China
- Southern Marine Science and Engineering, Guangdong Laboratory (Zhuhai), Zhuhai, PR China
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15
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Dai Y, Mak CM, Zhang Y, Cui D, Hang J. Investigation of interunit dispersion in 2D street canyons: A scaled outdoor experiment. BUILDING AND ENVIRONMENT 2020; 171:106673. [PMID: 32287993 PMCID: PMC7116958 DOI: 10.1016/j.buildenv.2020.106673] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2019] [Revised: 01/04/2020] [Accepted: 01/11/2020] [Indexed: 05/13/2023]
Abstract
Interunit dispersion problems have been studied previously mainly through on-site measurements, wind tunnel tests, and CFD simulations. In this study, a scaled outdoor experiment was conducted to examine the interunit dispersion characteristics in consecutive two-dimensional street canyons. Tracer gas ( C O 2 ) was continuously released to simulate the pollutant dispersion routes between the rooms in street canyons. The wind velocity, wind direction, air temperature, and tracer gas concentrations were monitored simultaneously. Two important parameters, the air exchange rate and reentry ratio, were analyzed to reveal the ventilation performance and interunit dispersion of the rooms in the street canyons. Based on the real-time weather conditions, it was found that the ventilation performance of the source room varied according to the room location. The air exchange rate distribution of the leeward-side room was more stable than that of the windward side. The tracer gas was mainly transported in the vortex direction inside the street canyon, and the highest reentry ratio was observed at the room nearest to the source room along the transportation route. In addition, under real weather conditions, the rooms in the street canyon have a high probability of experiencing a high reentry ratio based on the maximum reentry ratio of each room. This study provides authentic airflow and pollutant dispersion information in the street canyons in an urban environment. The dataset of this experiment can be used to validate further numerical simulations.
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Affiliation(s)
- Yuwei Dai
- Department of Building Services Engineering, The Hong Kong Polytechnic University, Hong Kong, PR China
| | - Cheuk Ming Mak
- Department of Building Services Engineering, The Hong Kong Polytechnic University, Hong Kong, PR China
- Corresponding author.
| | - Yong Zhang
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, 510275, PR China
| | - Dongjin Cui
- School of Architecture & Urban Planning, Shenzhen University, Shenzhen, 518060, PR China
| | - Jian Hang
- School of Atmospheric Sciences, Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies, Sun Yat-sen University, Guangzhou, 510275, PR China
- Southern Marine Science and Engineering, Guangdong Laboratory (Zhuhai), Zhuhai, PR China
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16
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Ai Z, Mak CM, Gao N, Niu J. Tracer gas is a suitable surrogate of exhaled droplet nuclei for studying airborne transmission in the built environment. BUILDING SIMULATION 2020; 13:489-496. [PMID: 32211124 PMCID: PMC7090680 DOI: 10.1007/s12273-020-0614-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Revised: 12/31/2019] [Accepted: 01/15/2020] [Indexed: 05/04/2023]
Affiliation(s)
- Zhengtao Ai
- Department of Building Environment and Energy, College of Civil Engineering, Hunan University, Changsha, China
| | - Cheuk Ming Mak
- Department of Building Services Engineering, The Hong Kong Polytechnic University, Hong Kong, China
| | - Naiping Gao
- School of Mechanical Engineering, Tongji University, Shanghai, China
| | - Jianlei Niu
- Department of Building Services Engineering, The Hong Kong Polytechnic University, Hong Kong, China
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17
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Jo S, Hong J, Lee SE, Ki M, Choi BY, Sung M. Airflow analysis of Pyeongtaek St Mary's Hospital during hospitalization of the first Middle East respiratory syndrome patient in Korea. ROYAL SOCIETY OPEN SCIENCE 2019; 6:181164. [PMID: 31031996 PMCID: PMC6458380 DOI: 10.1098/rsos.181164] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Accepted: 02/12/2019] [Indexed: 05/21/2023]
Abstract
Middle East respiratory syndrome (MERS) is known to be transmitted through close contact. However, epidemiological surveys of MERS in Korea indicated that some secondary patients were infected without close contact. Therefore, the possibility of other transmission routes must be identified. In this study, the possibility of MERS spreading through airflow was investigated on the eighth floor of Pyeongtaek St Mary's Hospital. Computational fluid dynamics was used to analyse the indoor airflow and passive tracer diffusion during the index patient's stay. Six cases were simulated for different outdoor wind directions and indoor mechanical ventilation operations. When a passive tracer was released in ward 8104, where the index patient was hospitalized, the passive tracer spread through the indoor airflow, which was created by the outdoor airflow. Ward 8109, which had the largest number of infected cases and was far distant from ward 8104, showed passive tracer concentration in all cases. This result indicates that MERS may have spread through airflow. The study results do not imply that the infection pathway of MERS is airborne. However, the results show the possibility of MERS spreading through airflow in specific environments such as poor ventilation environments.
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Affiliation(s)
- Seongmin Jo
- Department of Architectural Engineering, Sejong University, Seoul, South Korea
| | - Jinkwan Hong
- Department of HVAC and Firefighting Engineering, Gachon University, Gyeonggi-do, South Korea
| | - Sang-Eun Lee
- Division of Vectors and Parasitic Diseases, Korea Centers for Disease Control and Prevention, Cheongju, South Korea
| | - Moran Ki
- Department of Cancer Control and Population Health, Graduate School of Cancer Science and Policy, National Cancer Center, Goyang, South Korea
| | - Bo Youl Choi
- Department of Preventive Medicine, Hanyang University Medical College, Seoul, South Korea
| | - Minki Sung
- Department of Architectural Engineering, Sejong University, Seoul, South Korea
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18
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Sung M, Jo S, Lee SE, Ki M, Choi BY, Hong J. Airflow as a Possible Transmission Route of Middle East Respiratory Syndrome at an Initial Outbreak Hospital in Korea. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2018; 15:E2757. [PMID: 30563206 PMCID: PMC6313554 DOI: 10.3390/ijerph15122757] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/04/2018] [Revised: 11/24/2018] [Accepted: 12/04/2018] [Indexed: 12/28/2022]
Abstract
In this study, the results of an airflow investigation conducted on 7 June 2015 as part of a series of epidemiologic investigations at Pyeongtaek St. Mary's Hospital, South Korea, were investigated. The study involved 38 individuals who were infected directly and indirectly with Middle East Respiratory Syndrome (MERS), by a super-spreader patient. Tracer gas experiments conducted on the eighth floor, where the initial patient was hospitalized, confirmed that the tracer gas spread to adjacent patient rooms and rooms across corridors. In particular, the experiment with an external wind direction and speed similar to those during the hospitalization of the initial patient revealed that the air change rate was 17⁻20 air changes per hour (ACH), with air introduced through the window in the room of the infected patient (room 8104). The tracer gas concentration of room 8110, which was the farthest room, was 7.56% of room 8104, indicating that a high concentration of gas has spread from room 8104 to rooms across the corridor. In contrast, the tracer gas was barely detected in a maternity ward to the south of room 8104, where there was no secondary infected patient. Moreover, MERS is known to spread mainly by droplets through close contact, but long-distance dispersion is probable in certain environments, such as that of a super-spreader patient hospitalized in a room without ventilation, hospitals with a central corridor type, and indoor airflow dispersion due to external wind.
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Affiliation(s)
- Minki Sung
- Department of Architectural Engineering, Sejong University, 209, Seoul 05006, Korea.
| | - Seongmin Jo
- Department of Architectural Engineering, Sejong University, 209, Seoul 05006, Korea.
| | - Sang-Eun Lee
- Division of Vectors and Parasitic Diseases, Korea Centers for Disease Control and Prevention, Cheongju 28159, Korea.
| | - Moran Ki
- Department of Cancer Control and Population Health, Graduate School of Cancer Science and Policy, National Cancer Center, Goyang 10408, Korea.
| | - Bo Youl Choi
- Department of Preventive Medicine, Hanyang University Medical College, Seoul 04763, Korea.
| | - JinKwan Hong
- Department of HVAC & Firefighting Engineering, Gachon University, Seongnam 13120, Korea.
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19
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Ai ZT, Melikov AK. Airborne spread of expiratory droplet nuclei between the occupants of indoor environments: A review. INDOOR AIR 2018; 28:500-524. [PMID: 29683213 DOI: 10.1111/ina.12465] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2017] [Accepted: 04/13/2018] [Indexed: 05/04/2023]
Abstract
This article reviews past studies of airborne transmission between occupants in indoor environments, focusing on the spread of expiratory droplet nuclei from mouth/nose to mouth/nose for non-specific diseases. Special attention is paid to summarizing what is known about the influential factors, the inappropriate simplifications of the thermofluid boundary conditions of thermal manikins, the challenges facing the available experimental techniques, and the limitations of available evaluation methods. Secondary issues are highlighted, and some new ways to improve our understanding of airborne transmission indoors are provided. The characteristics of airborne spread of expiratory droplet nuclei between occupants, which are influenced correlatively by both environmental and personal factors, were widely revealed under steady-state conditions. Owing to the different boundary conditions used, some inconsistent findings on specific influential factors have been published. The available instrumentation was too slow to provide accurate concentration profiles for time-dependent evaluations of events with obvious time characteristics, while computational fluid dynamics (CFD) studies were mainly performed in the framework of inherently steady Reynolds-averaged Navier-Stokes modeling. Future research needs in 3 areas are identified: the importance of the direction of indoor airflow patterns, the dynamics of airborne transmission, and the application of CFD simulations.
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Affiliation(s)
- Z T Ai
- Department of Civil Engineering, International Centre for Indoor Environment and Energy, Technical University of Denmark, Copenhagen, Denmark
| | - A K Melikov
- Department of Civil Engineering, International Centre for Indoor Environment and Energy, Technical University of Denmark, Copenhagen, Denmark
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20
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Wang J, Zhang T, Wang S, Battaglia F. Gaseous pollutant transmission through windows between vertical floors in a multistory building with natural ventilation. ENERGY AND BUILDINGS 2017; 153:325-340. [PMID: 32288118 PMCID: PMC7127727 DOI: 10.1016/j.enbuild.2017.08.025] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Revised: 07/25/2017] [Accepted: 08/09/2017] [Indexed: 05/19/2023]
Abstract
Natural ventilation is an effective strategy to control thermal comfort in buildings, and can be enhanced depending on the window style. The combination of natural ventilation and window can also facilitate the removal or dilution of gaseous pollutants from indoor sources in newly decorated buildings. However, the windows on the same facade may cause gaseous pollutant cross-transmission during single-sided natural ventilation between households on different floors close to the source. Although some research has focused on the pollutant cross-transmission in buildings, the simplification of windows into rectangular openings often affects accurate knowledge of pollutant transmission characteristics. Therefore, this investigation explored gaseous pollutant cross-transmission through real windows during single-sided, buoyancy-driven ventilation in a multistory building. Six types of windows were modeled for the indoor pollutant of gaseous formaldehyde (HCHO). Computational fluid dynamics (CFD) was utilized to solve characteristics of pollutant transmission inside and outside the multistory building. The results indicated that the ventilation rates, thermal profiles and pollutant transmission inside and outside the building varied for each window type, although the open window areas were identical. The re-entry ratio of exhausted air entering upper floors and the infection risk of epidemic viruses caused by airborne cross-transmission was sensitive to ventilation rates and window configurations, while the sensitivities for window configurations varied case by case. The comparisons also revealed that the specification of ambient temperature and pollutant release rate ultimately did not affect the evaluation of pollutant cross-transmission using CFD.
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Affiliation(s)
- Jihong Wang
- School of Civil Engineering, Dalian University of Technology, 2 Linggong Road, Dalian 116024, China
- Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, 635 Prices Fork Road, Blacksburg, VA 24061, USA
| | - Tengfei Zhang
- School of Civil Engineering, Dalian University of Technology, 2 Linggong Road, Dalian 116024, China
| | - Shugang Wang
- School of Civil Engineering, Dalian University of Technology, 2 Linggong Road, Dalian 116024, China
| | - Francine Battaglia
- Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, 635 Prices Fork Road, Blacksburg, VA 24061, USA
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21
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Yan Y, Li X, Shang Y, Tu J. Evaluation of airborne disease infection risks in an airliner cabin using the Lagrangian-based Wells-Riley approach. BUILDING AND ENVIRONMENT 2017; 121:79-92. [PMID: 32287972 PMCID: PMC7111330 DOI: 10.1016/j.buildenv.2017.05.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Revised: 04/28/2017] [Accepted: 05/08/2017] [Indexed: 05/03/2023]
Abstract
An urgent demand of assessing passengers' exposure risks in airliner cabins was raised as commercial airliners are one of the major media that carrying and transmitting infectious disease worldwide. In this study, simulations were conducted using a Boeing 737 cabin model to study the transport characteristics of airborne droplets and the associated infection risks of passengers. The numerical results of the airflow field were firstly compared against the experimental data in the literature to validate the reliability of the simulations. Airborne droplets were assumed to be released by passengers through coughing and their transport characteristics were modelled using the Lagrangian approach. Numerical results found that the particle travel distance was very sensitive to the release locations, and the impact was more significant along the longitudinal and horizontal directions. Particles released by passengers sitting next to the windows could travel much further than the others. A quantifiable approach was then applied to assess the individual infection risks of passengers. The key particle transport information such as the particle residence time yielded from the Lagrangian tracking process was extracted and integrated into the Wells-Riley equation to estimate the risks of infection. Compared to the Eulerian-based approach, the Lagrangian-based approach presented in this study is more robust as it addresses both the particle concentration and particle residence time in the breathing zone of every individual passenger.
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Affiliation(s)
- Yihuan Yan
- School of Engineering, RMIT University, PO Box 71, Bundoora, VIC 3083, Australia
| | - Xiangdong Li
- School of Engineering, RMIT University, PO Box 71, Bundoora, VIC 3083, Australia
| | - Yidan Shang
- School of Engineering, RMIT University, PO Box 71, Bundoora, VIC 3083, Australia
| | - Jiyuan Tu
- School of Engineering, RMIT University, PO Box 71, Bundoora, VIC 3083, Australia
- Key Laboratory of Ministry of Education for Advanced Reactor Engineering and Safety, Institute of Nuclear and New Energy Technology, Tsinghua University, PO Box 1021, Beijing 100086, China
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22
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Wu Y, Niu J, Liu X. Air infiltration induced inter-unit dispersion and infectious risk assessment in a high-rise residential building. BUILDING SIMULATION 2017; 11:193-202. [PMID: 32218902 PMCID: PMC7090850 DOI: 10.1007/s12273-017-0388-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Revised: 05/24/2017] [Accepted: 06/05/2017] [Indexed: 05/03/2023]
Abstract
Identifying possible airborne transmission routes and assessing the associated infectious risks are essential for implementing effective control measures. This study focuses on the infiltration-induced inter-unit pollutant dispersion in a high-rise residential (HRR) building. The outdoor wind pressure distribution on the building facades was obtained from the wind tunnel experiments. And the inter-household infiltration and tracer gas transmission were simulated using multi-zone model. The risk levels along building height and under different wind directions were examined, and influence of component leakage area was analysed. It is found that, the cross-infection risk can be over 20% because of the low air infiltration rate below 0.7 ACH, which is significantly higher than the risk of 9% obtained in our previous on-site measurement with air change rate over 3 ACH. As the air infiltration rate increases along building height, cross-infection risk is generally higher on the lower floors. The effect of wind direction on inter-unit dispersion level is significant, and the presence of a contaminant source in the windward side results in the highest cross-infection risks in other adjacent units on the same floor. Properly improving internal components tightness and increasing air change via external components are beneficial to the control of internal inter-unit transmission induced by infiltration. However, this approach may increase the cross-infection via the external transmission, and effective control measures should be further explored considering multiple transmission routes.
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Affiliation(s)
- Yan Wu
- Department of Building Services Engineering, The Hong Kong Polytechnic University, Hong Kong, China
| | - Jianlei Niu
- Faculty of Architecture, Design and Planning, The University of Sydney, Sydney, Australia
| | - Xiaoping Liu
- School of Civil Engineering, HeFei University of Technology, HeFei, China
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23
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Mu D, Gao N, Zhu T. Wind tunnel tests of inter-flat pollutant transmission characteristics in a rectangular multi-storey residential building, part A: Effect of wind direction. BUILDING AND ENVIRONMENT 2016; 108:159-170. [PMID: 32287967 PMCID: PMC7111322 DOI: 10.1016/j.buildenv.2016.08.032] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Revised: 08/28/2016] [Accepted: 08/29/2016] [Indexed: 05/07/2023]
Abstract
The inter-flat dispersion of hazardous air pollutants in residential built environment has become a growing concern, especially in crowed urban areas. The purpose of present study is to investigate the wind induced air pollutant transmission and cross contamination routes in typical buildings. In this paper, a series of experiments was carried out in a boundary layer wind tunnel using a 1:30 scaled model that represented the typical configuration of rectangular multi-storey residential buildings in Shanghai. Sulfur hexafluoride (SF6) was employed as tracer gas in the wind tunnel tests. The conditions under two ventilation modes, i.e. single-sided natural ventilation and cross natural ventilation, were compared. The tracer gas concentration distributions under four approaching wind angles were monitored and analyzed. Computational Fluid Dynamics (CFD) method was adopted to assist in analyzing airflow patterns. The experiment results elucidated that in the two ventilation scenarios, both of the vertical and horizontal inter-flat airborne transmission could proceed. The wind direction played a key role on the pollutant concentration distribution. Compared with the single-sided ventilation mode, cross ventilation could weaken the air pollutant dispersion along the vertical direction when the contamination source was on the windward or on the leeward unit. When the wind blowing parallelly to the source unit window, namely the source room was on the sideward, cross ventilation would not suppress the vertical transport on one hand, but reinforce the horizontal transmission on the other hand. The study is helpful for the analysis of infection risk of respiratory diseases in the residential buildings.
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Affiliation(s)
- Di Mu
- School of Mechanical Engineering, Tongji University, Shanghai, China
| | - Naiping Gao
- School of Mechanical Engineering, Tongji University, Shanghai, China
| | - Tong Zhu
- School of Mechanical Engineering, Tongji University, Shanghai, China
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24
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Mu D, Gao N, Zhu T. Wind tunnel tests of inter-flat pollutant transmission characteristics in a rectangular multi-storey residential building, part A: Effect of wind direction. BUILDING AND ENVIRONMENT 2016; 108:159-170. [PMID: 32287967 DOI: 10.1016/j.buildenv.2016.08032] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Revised: 08/28/2016] [Accepted: 08/29/2016] [Indexed: 05/22/2023]
Abstract
The inter-flat dispersion of hazardous air pollutants in residential built environment has become a growing concern, especially in crowed urban areas. The purpose of present study is to investigate the wind induced air pollutant transmission and cross contamination routes in typical buildings. In this paper, a series of experiments was carried out in a boundary layer wind tunnel using a 1:30 scaled model that represented the typical configuration of rectangular multi-storey residential buildings in Shanghai. Sulfur hexafluoride (SF6) was employed as tracer gas in the wind tunnel tests. The conditions under two ventilation modes, i.e. single-sided natural ventilation and cross natural ventilation, were compared. The tracer gas concentration distributions under four approaching wind angles were monitored and analyzed. Computational Fluid Dynamics (CFD) method was adopted to assist in analyzing airflow patterns. The experiment results elucidated that in the two ventilation scenarios, both of the vertical and horizontal inter-flat airborne transmission could proceed. The wind direction played a key role on the pollutant concentration distribution. Compared with the single-sided ventilation mode, cross ventilation could weaken the air pollutant dispersion along the vertical direction when the contamination source was on the windward or on the leeward unit. When the wind blowing parallelly to the source unit window, namely the source room was on the sideward, cross ventilation would not suppress the vertical transport on one hand, but reinforce the horizontal transmission on the other hand. The study is helpful for the analysis of infection risk of respiratory diseases in the residential buildings.
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Affiliation(s)
- Di Mu
- School of Mechanical Engineering, Tongji University, Shanghai, China
| | - Naiping Gao
- School of Mechanical Engineering, Tongji University, Shanghai, China
| | - Tong Zhu
- School of Mechanical Engineering, Tongji University, Shanghai, China
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