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Berlanga FA, Gomez P, Esteban A, Liu L, Nielsen PV. Three dimensional analysis of the exhalation flow in the proximity of the mouth. Heliyon 2024; 10:e26283. [PMID: 38434078 PMCID: PMC10906307 DOI: 10.1016/j.heliyon.2024.e26283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 02/02/2024] [Accepted: 02/09/2024] [Indexed: 03/05/2024] Open
Abstract
The human exhalation flow is characterized in this work from the three-dimensional velocimetry results obtained by using the stereo particle image velocimetry (SPIV) measurement technique on the flow emitted from a realistic airway model. For this purpose, the transient exhalation flow through the mouth of a person performing two different breaths corresponding to two metabolic rates, standing relaxed (SR) and walking active (WA), is emulated and studied. To reproduce the flow realistically, a detailed three-dimensional model obtained from computed tomography measurements on real subjects is used. To cope with the variability of the experimental data, a subsequent analysis of the results is performed using the TR-PIV (time resolved particle image velocimetry) technique. Exhalation produces a transient jet that becomes a puff when flow emission ends. Three-dimensional vector fields of the jet velocity are obtained in five equally spaced transverse planes up to a distance of Image 1 from the mouth at equally spaced time instants Image 2 which will be referred to as phases (φ), from the beginning to the end of exhalation. The time evolution during exhalation of the jet area of influence, the velocity field and the jet air entrainment have been characterized for each of the jet cross sections. The importance of the use of realistic airway models for the study of this type of flow and the influence of the metabolic rate on its development are also analyzed. The results obtained contribute to the characterization of the human exhalation as a pathway of the transmission of pathogens such as SARS-CoV-2 virus.
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Affiliation(s)
- F A Berlanga
- Dept. de Mecánica, ETSII, Universidad Nacional de Educación a Distancia (UNED), E-28040, Madrid, Spain
| | - P Gomez
- Dept. de Mecánica, ETSII, Universidad Nacional de Educación a Distancia (UNED), E-28040, Madrid, Spain
| | - A Esteban
- Dept. de Mecánica, ETSII, Universidad Nacional de Educación a Distancia (UNED), E-28040, Madrid, Spain
| | - L Liu
- Dept. of Building Science and Technology, School of Architecture, Tsinghua University, Haidian District, Beijing, China
| | - P V Nielsen
- Dept. of the Built Environment, Aalborg Universitet, Thomas Manns Vej 23 9220 Aalborg Øst, Denmark
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2
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Jung SS. Simplified models of aerosol collision and deposition for disease transmission. Sci Rep 2023; 13:20778. [PMID: 38012339 PMCID: PMC10682024 DOI: 10.1038/s41598-023-48053-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Accepted: 11/21/2023] [Indexed: 11/29/2023] Open
Abstract
Fluid-mechanics research has focused primarily on droplets/aerosols being expelled from infected individuals and transmission of well-mixed aerosols indoors. However, aerosol collisions with susceptible hosts earlier in the spread, as well as aerosol deposition in the nasal cavity, have been relatively overlooked. In this paper, two simple fluid models are presented to gain a better understanding of the collision and deposition between a human and aerosols. The first model is based on the impact of turbulent diffusion coefficients and air flow in a room on the collisions between aerosols and humans. Infection rates can be determined based on factors such as air circulation and geometry as an infection zone expands from an infected host. The second model clarifies how aerosols of different sizes adhere to different parts of the respiratory tract. Based on the inhalation rate and the nasal cavity shape, the critical particle size and the deposition location can be determined. Our study offers simple fluid models to understand the effects of geometric factors and air flows on the aerosol transmission and deposition.
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Affiliation(s)
- Sunghwan Sunny Jung
- Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY, 14853, USA.
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3
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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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4
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Norvihoho LK, Yin J, Zhou ZF, Han J, Chen B, Fan LH, Lichtfouse E. Mechanisms controlling the transport and evaporation of human exhaled respiratory droplets containing the severe acute respiratory syndrome coronavirus: a review. ENVIRONMENTAL CHEMISTRY LETTERS 2023; 21:1701-1727. [PMID: 36846189 PMCID: PMC9944801 DOI: 10.1007/s10311-023-01579-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Accepted: 02/13/2023] [Indexed: 05/24/2023]
Abstract
Transmission of the coronavirus disease 2019 is still ongoing despite mass vaccination, lockdowns, and other drastic measures to control the pandemic. This is due partly to our lack of understanding on the multiphase flow mechanics that control droplet transport and viral transmission dynamics. Various models of droplet evaporation have been reported, yet there is still limited knowledge about the influence of physicochemical parameters on the transport of respiratory droplets carrying the severe acute respiratory syndrome coronavirus 2. Here we review the effects of initial droplet size, environmental conditions, virus mutation, and non-volatile components on droplet evaporation and dispersion, and on virus stability. We present experimental and computational methods to analyze droplet transport, and factors controlling transport and evaporation. Methods include thermal manikins, flow techniques, aerosol-generating techniques, nucleic acid-based assays, antibody-based assays, polymerase chain reaction, loop-mediated isothermal amplification, field-effect transistor-based assay, and discrete and gas-phase modeling. Controlling factors include environmental conditions, turbulence, ventilation, ambient temperature, relative humidity, droplet size distribution, non-volatile components, evaporation and mutation. Current results show that medium-sized droplets, e.g., 50 µm, are sensitive to relative humidity. Medium-sized droplets experience delayed evaporation at high relative humidity, and increase airborne lifetime and travel distance. By contrast, at low relative humidity, medium-sized droplets quickly shrink to droplet nuclei and follow the cough jet. Virus inactivation within a few hours generally occurs at temperatures above 40 °C, and the presence of viral particles in aerosols impedes droplet evaporation.
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Affiliation(s)
- Leslie Kojo Norvihoho
- State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an, 710049 Shaanxi People’s Republic of China
| | - Jing Yin
- State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an, 710049 Shaanxi People’s Republic of China
| | - Zhi-Fu Zhou
- State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an, 710049 Shaanxi People’s Republic of China
| | - Jie Han
- School of Human Settlements and Civil Engineering, Xi’an Jiaotong University, Xi’an, 710049 Shaanxi People’s Republic of China
| | - Bin Chen
- State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an, 710049 Shaanxi People’s Republic of China
| | - Li-Hong Fan
- The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, 710061 Shaanxi People’s Republic of China
| | - Eric Lichtfouse
- State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an, 710049 Shaanxi People’s Republic of China
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5
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Rahvard AJ, Karami S, Lakzian E. Finding the proper position of supply and return registers of air condition system in a conference hall in term of COVID-19 virus spread. REVUE INTERNATIONALE DU FROID 2023; 145:78-89. [PMID: 36281435 PMCID: PMC9581653 DOI: 10.1016/j.ijrefrig.2022.10.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Revised: 10/10/2022] [Accepted: 10/14/2022] [Indexed: 06/16/2023]
Abstract
The outbreak of the COVID-19 has affected all aspects of people's lives around the world. As air transmits the viruses, air-conditioning systems in buildings, surrounded environments, and public transport have a significant role in restricting the transmission of airborne pathogens. In this paper, a computational fluid dynamic (CFD) model is deployed to simulate the dispersion of the COVID-19 virus due to the coughing of a patient in a conference hall, and the effect of displacement of supply and return registers of the air conditioning system is investigated. A validated Eulerian-Lagrangian CFD model is used to simulate the airflow in the conference hall. The particles created by coughing are droplets of the patient's saliva that contain the virus. Three cases with different positions of supply and return registers have been compared. The simulation results show that case1 has the best performance; since after 80 s in case 1 that the inlet registers are in the longitudinal wall, the whole particles are removed from space. However, in other cases, some particles are still in space.
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Affiliation(s)
- Ahmad Jahani Rahvard
- Center of Computational Energy, Department of Mechanical Engineering, Hakim Sabzevari University, Sabzevar, Iran
| | - Shahram Karami
- Center of Computational Energy, Department of Mechanical Engineering, Hakim Sabzevari University, Sabzevar, Iran
| | - Esmail Lakzian
- Center of Computational Energy, Department of Mechanical Engineering, Hakim Sabzevari University, Sabzevar, Iran
- Department of Environmental Safety and Product Quality Management, Institute of Environmental Engineering, Peoples' Friendship University of Russia (RUDN University), 6 Miklukho-Maklaya Street, Moscow, 117198 Russia
- Department of Mechanical Engineering, Andong National University, Andong, South Korea
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6
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Nie Z, Chen Y, Deng M. Quantitative evaluation of precautions against the COVID-19 indoor transmission through human coughing. Sci Rep 2022; 12:22573. [PMID: 36585431 PMCID: PMC9803700 DOI: 10.1038/s41598-022-26837-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2022] [Accepted: 12/21/2022] [Indexed: 12/31/2022] Open
Abstract
In this work, we focus on the dispersion of COVID-19-laden droplets using the transient computational fluid dynamics (CFD) modeling and simulation of the coughing process of virus carriers in an enclosure room, aiming to set up the basic prototype of popular precautionary strategies, i.e., face mask, upward ventilation, protective screen, or any combination thereof, against the indoor transmission of COVID-19 and other highly contagious diseases in the future. A multi-component Eulerian-Lagrangian CFD particle-tracking model with user-defined functions is utilized under 8 cases to examine the characteristics of droplet dispersion concerning the mass and heat transfer, droplet evaporation, air buoyancy, air convection, air-droplet friction, and turbulent dispersion. The result shows that implementing upward ventilation is the most effective measure, followed by wearing face masks. Protective screens can restrict the movement of the coughing droplets (though it will not reduce viral load). However, applying protective screens arranged with lean can be counterproductive in preventing the spread of COVID-19 when it is inappropriately placed with ventilation. The soundest solution is the combination of the face mask and upward ventilation, which can reduce the indoor infectious concentration by nearly 99.95% compared with the baseline without any precautionary strategies. With the resumption of school and work in the post-epidemic era, this study would provide intelligence-enhancing advice for the masses and rule-makers to curb the pandemic.
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Affiliation(s)
- Zhenguo Nie
- grid.12527.330000 0001 0662 3178Department of Mechanical Engineering, Tsinghua University, Beijing, 100084 China ,State Key Laboratory of Tribology in Advanced Equipment, Beijing, 100084 China ,Beijing Key Lab of Precision/Ultra-precision Manufacturing Equipments and Control, Beijing, 100084 China
| | - Yunzhi Chen
- grid.12527.330000 0001 0662 3178Department of Mechanical Engineering, Tsinghua University, Beijing, 100084 China ,grid.440686.80000 0001 0543 8253Marine Engineering College, Dalian Maritime University, Dalian, 116026 Liaoning China
| | - Meifeng Deng
- grid.9227.e0000000119573309State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093 China ,grid.410726.60000 0004 1797 8419University of Chinese Academy of Sciences, Beijing, 100049 China
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7
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Oh W, Ooka R, Kikumoto H, Han M. Numerical modeling of sneeze airflow and its validation with an experimental dataset. INDOOR AIR 2022; 32:e13171. [PMID: 36437664 DOI: 10.1111/ina.13171] [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: 10/04/2022] [Revised: 10/24/2022] [Accepted: 10/25/2022] [Indexed: 06/16/2023]
Abstract
In this study, we aimed at providing datasets using experimental results to validate the sneeze airflow. In addition, the boundary conditions for the sneeze simulation that could reproduce the sneeze airflow in the experimental results are presented and reviewed. The validation datasets were created by performing ensemble-average analysis with the experimental results of particle image velocimetry, and these were used to explore the boundary conditions to reproduce the sneeze airflow. As a result of the sneeze airflow reproduced by computational fluid dynamics simulation, the magnitude ranges of maximum velocity at the interface were observed to be 21.1-23.9 m/s for males and 17.9-20.3 m/s for females, which were higher than those of coughing. Compared with the experimental results, the root-mean-square error range for the overall airflow distribution was 0.19-0.23 m/s, whereas the error range for the magnitude of the maximum velocity at a criterion point was 0.03-0.08 m/s. The total sneezing airflow volume was in the range of 0.36-0.48 L, which was relatively low compared with that of coughing. Thus, this study provides important fundamental boundary conditions for computational fluid dynamics analysis, validated by experimental results, to interpret the spread of infectious particles by sneezing.
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Affiliation(s)
- Wonseok Oh
- Institute of Industrial Science, The University of Tokyo, Tokyo, Japan
| | - Ryozo Ooka
- Institute of Industrial Science, The University of Tokyo, Tokyo, Japan
| | - Hideki Kikumoto
- Institute of Industrial Science, The University of Tokyo, Tokyo, Japan
| | - Mengtao Han
- School of Architecture and Urban Planning, Huazhong University of Science and Technology, Wuhan, China
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8
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Liu Z, Yao G, Li Y, Huang Z, Jiang C, He J, Wu M, Liu J, Liu H. Bioaerosol distribution characteristics and potential SARS-CoV-2 infection risk in a multi-compartment dental clinic. BUILDING AND ENVIRONMENT 2022; 225:109624. [PMID: 36164582 PMCID: PMC9494923 DOI: 10.1016/j.buildenv.2022.109624] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/04/2022] [Revised: 08/28/2022] [Accepted: 09/17/2022] [Indexed: 06/16/2023]
Abstract
Dental clinics have a potential risk of infection, particularly during the COVID-19 pandemic. Multi-compartment dental clinics are widely used in general hospitals and independent clinics. This study utilised computational fluid dynamics to investigate the bioaerosol distribution characteristics in a multi-compartment dental clinic through spatiotemporal distribution, working area time-varying concentrations, and key surface deposition. The infection probability of SARS-CoV-2 for the dental staff and patients was calculated using the Wells-Riley model. In addition, the accuracy of the numerical model was verified by field measurements of aerosol concentrations performed during a clinical ultrasonic scaling procedure. The results showed that bioaerosols were mainly distributed in the compartments where the patients were treated. The average infection probability was 3.8% for dental staff. The average deposition number per unit area of the treatment chair and table are 28729 pcs/m2 and 7945 pcs/m2, respectively, which creates a possible contact transmission risk. Moreover, there was a certain cross-infection risk in adjacent compartments, and the average infection probability for patients was 0.84%. The bioaerosol concentrations of the working area in each compartment 30 min post-treatment were reduced to 0.07% of those during treatment, and the infection probability was <0.05%. The results will contribute to an in-depth understanding of the infection risk in multi-compartment dental clinics, forming feasible suggestions for management to efficiently support epidemic prevention and control in dental clinics.
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Affiliation(s)
- Zhijian Liu
- Department of Power Engineering, North China Electric Power University, Baoding, Hebei, 071003, PR China
| | - Guangpeng Yao
- Department of Power Engineering, North China Electric Power University, Baoding, Hebei, 071003, PR China
| | - Yabin Li
- The Fifth Medical Center of PLA General Hospital, Beijing, 100039, China
| | - Zhenzhe Huang
- Department of Power Engineering, North China Electric Power University, Baoding, Hebei, 071003, PR China
| | - Chuan Jiang
- Department of Power Engineering, North China Electric Power University, Baoding, Hebei, 071003, PR China
| | - Junzhou He
- Department of Power Engineering, North China Electric Power University, Baoding, Hebei, 071003, PR China
| | - Minnan Wu
- Department of Power Engineering, North China Electric Power University, Baoding, Hebei, 071003, PR China
| | - Jia Liu
- The Fifth Medical Center of PLA General Hospital, Beijing, 100039, China
| | - Haiyang Liu
- Department of Power Engineering, North China Electric Power University, Baoding, Hebei, 071003, PR China
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9
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Ahmadzadeh M, Shams M. A numerical approach for preventing the dispersion of infectious disease in a meeting room. Sci Rep 2022; 12:16959. [PMID: 36217014 PMCID: PMC9549042 DOI: 10.1038/s41598-022-21161-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Accepted: 09/23/2022] [Indexed: 12/29/2022] Open
Abstract
Airborne transmission of respiratory aerosols carrying infectious viruses has generated many concerns about cross-contamination risks, particularly in indoor environments. ANSYS Fluent software has been used to investigate the dispersion of the viral particles generated during a coughing event and their transport dynamics inside a safe social-distance meeting room. Computational fluid dynamics based on coupled Eulerian-Lagrangian techniques are used to explore the characteristics of the airflow field in the domain. The main objective of this study is to investigate the effects of the window opening frequency, exhaust layouts, and the location of the air conditioner systems on the dispersion of the particles. The results show that reducing the output capacity by raising the concentration of suspended particles and increasing their traveled distance caused a growth in the individuals' exposure to contaminants. Moreover, decreasing the distance between the ventilation systems installed location and the ceiling can drop the fraction of the suspended particles by over 35%, and the number of individuals who are subjected to becoming infected by viral particles drops from 6 to 2. As well, the results demonstrated when the direction of input airflow and generated particles were the same, the fraction of suspended particles of 4.125%, whereas if the inputs were shifted to the opposite direction of particle injection, the fraction of particles in fluid increased by 5.000%.
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Affiliation(s)
- Mahdi Ahmadzadeh
- grid.411976.c0000 0004 0369 2065Faculty of Mechanical Engineering, K. N. Toosi University of Technology, Pardis St., Vanak Sq., Tehran, Iran
| | - Mehrzad Shams
- grid.411976.c0000 0004 0369 2065Faculty of Mechanical Engineering, K. N. Toosi University of Technology, Pardis St., Vanak Sq., Tehran, Iran
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10
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Zhen Q, Zhang A, Huang Q, Li J, Du Y, Zhang Q. Overview of the Role of Spatial Factors in Indoor SARS-CoV-2 Transmission: A Space-Based Framework for Assessing the Multi-Route Infection Risk. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2022; 19:11007. [PMID: 36078723 PMCID: PMC9518419 DOI: 10.3390/ijerph191711007] [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: 07/26/2022] [Revised: 08/29/2022] [Accepted: 08/29/2022] [Indexed: 06/15/2023]
Abstract
The COVID-19 pandemic has lasted from 2019 to 2022, severely disrupting human health and daily life. The combined effects of spatial, environmental, and behavioral factors on indoor COVID-19 spread and their interactions are usually ignored. Especially, there is a lack of discussion on the role of spatial factors in reducing the risk of virus transmission in complex and diverse indoor environments. This paper endeavours to summarize the spatial factors and their effects involved in indoor virus transmission. The process of release, transport, and intake of SARS-CoV-2 was reviewed, and six transmission routes according to spatial distance and exposure way were classified. The triangular relationship between spatial, environmental and occupant behavioral parameters during virus transmission was discussed. The detailed effects of spatial parameters on droplet-based, surface-based and air-based transmission processes and virus viability were summarized. We found that spatial layout, public-facility design and openings have a significant indirect impact on the indoor virus distribution and transmission by affecting occupant behavior, indoor airflow field and virus stability. We proposed a space-based indoor multi-route infection risk assessment framework, in which the 3D building model containing detailed spatial information, occupant behavior model, virus-spread model and infection-risk calculation model are linked together. It is also applicable to other, similar, respiratory infectious diseases such as SARS, influenza, etc. This study contributes to developing building-level, infection-risk assessment models, which could help building practitioners make better decisions to improve the building's epidemic-resistance performance.
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Affiliation(s)
- Qi Zhen
- School of Architecture, Tianjin University, Tianjin 300072, China
| | - Anxiao Zhang
- School of Architecture, Tianjin University, Tianjin 300072, China
| | - Qiong Huang
- School of Architecture, Tianjin University, Tianjin 300072, China
| | - Jing Li
- Department of Epidemiology and Biostatistics, School of Public Health, Tianjin Medical University, Tianjin 300072, China
| | - Yiming Du
- School of Architecture, Tianjin University, Tianjin 300072, China
| | - Qi Zhang
- School of Architecture, Tianjin University, Tianjin 300072, China
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11
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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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12
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Transport Characteristics and Transmission Risk of Virus-Containing Droplets from Coughing in Outdoor Windy Environment. TOXICS 2022; 10:toxics10060294. [PMID: 35736903 PMCID: PMC9230890 DOI: 10.3390/toxics10060294] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Revised: 05/26/2022] [Accepted: 05/27/2022] [Indexed: 12/23/2022]
Abstract
Particle dispersions have been widely studied inside rooms, but few databases have examined the transmission risk of respiratory droplets outdoors. This study investigated the wind effect on the dispersion of coughed droplets and the influence of social distancing on the infection risk in different susceptible persons using computational fluid dynamics simulations. Infection risk was evaluated based on direct depositions and exposure fractions. The results indicated that a reverse and upward flow formed in front of an infected man, and it enhanced as the wind strengthened, which transported more medium particles higher and increased the deposition on both infected and susceptible persons. Small particles moved above the neck, and they rarely deposited on the body. Medium particles larger than 60 μm were more likely to deposit and could reach the head of a healthy person under stronger winds. The exposure fraction achieved peak values when numerous particles passed the breathing zone. Although longer social distancing could alleviate the particle deposition on the face and delay the most dangerous time, its effect on infection risk was ambiguous. The infection risk was larger for a shorter susceptible person because more particles were deposited on the face, and the exposure fraction contributed by particles above the neck was larger.
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Bahl P, de Silva C, MacIntyre CR, Bhattacharjee S, Chughtai AA, Doolan C. Flow dynamics of droplets expelled during sneezing. PHYSICS OF FLUIDS (WOODBURY, N.Y. : 1994) 2021; 33:111901. [PMID: 34803362 PMCID: PMC8597717 DOI: 10.1063/5.0067609] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Accepted: 10/09/2021] [Indexed: 05/15/2023]
Abstract
Respiratory infections transmit through droplets and aerosols generated by the infected individual during respiratory emissions. It is essential to study the flow dynamics of these emissions to develop strategies for mitigating the risk of infection. In particular, the dynamics of droplets expelled during violent exhalations such as sneezing is crucial, but has received little attention to date. Here, for the first time, we present the results of droplet dynamics of 35 sneezes, obtained from four volunteers, using particle tracking velocimetry experiments. Our results reveal a mean droplet velocity of 2-5.4 m/s across the different subjects. These values are significantly lower than what is usually assumed in the studies simulating or replicating sneezes. Furthermore, the large variation in droplet speeds, flow direction, spread angle, and head movement is also quantified. These findings will enable the refinement of models and simulations of sneezes toward improving infection control guidelines.
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Affiliation(s)
- Prateek Bahl
- School of Mechanical and Manufacturing Engineering, UNSW Sydney, Kensington NSW 2052, Australia
| | - Charitha de Silva
- School of Mechanical and Manufacturing Engineering, UNSW Sydney, Kensington NSW 2052, Australia
| | - C. Raina MacIntyre
- Biosecurity Program, The Kirby Institute, UNSW Sydney, Kensington, NSW 2052, Australia
| | - Shovon Bhattacharjee
- Biosecurity Program, The Kirby Institute, UNSW Sydney, Kensington, NSW 2052, Australia
| | | | - Con Doolan
- School of Mechanical and Manufacturing Engineering, UNSW Sydney, Kensington NSW 2052, Australia
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Han M, Ooka R, Kikumoto H, Oh W, Bu Y, Hu S. Experimental measurements of airflow features and velocity distribution exhaled from sneeze and speech using particle image velocimetry. BUILDING AND ENVIRONMENT 2021; 205:108293. [PMID: 34908645 PMCID: PMC8663001 DOI: 10.1016/j.buildenv.2021.108293] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 08/24/2021] [Accepted: 08/24/2021] [Indexed: 05/19/2023]
Abstract
Airflow exhaled from sneeze and speech is an important source of viruses and droplets in daily life and may cause imperceptible virus propagation. The velocities of sneeze and speech airflow exhaled from 10 healthy young participants repeatedly using high-frequency (2986 Hz) particle image velocimetry are measured. The parameters for describing the dynamic process of sneeze airflow, such as sneeze duration time (SDT), peak velocity time (PVT), maximum velocities, and sneeze spread angle, are analyzed. The sneeze airflow lasts 430 ms (SDT) and reaches the peak velocity in the first 20 ms (PVT). The maximum sneeze airflow velocity is approximately 15.9 m/s. The temporal variation of the sneeze velocity exhibits the gamma distribution. For speech airflow, the maximum instantaneous velocity and maximum time-averaged velocity are reported. The maximum instantaneous velocity is approximately 6.25 m/s, whereas the time-averaged value is only 0.208 m/s owing to the extremely small airflow velocity among syllables. The vertical/horizontal spread angles of the airflow are 15.1°/15.4° for sneeze and 52.9°/42.9° for speech. The difference in airflow features based on gender is generally slight for both sneeze and speech. Subsequently, an ensemble-average operation is conducted to obtain the general and representative velocity distributions. We report each component of the temporal and spatial velocity distributions of the sneeze airflow and the time-averaged velocity distribution of the speech airflow. These detailed distribution data can provide a comprehensive understanding of sneeze and speech airflow movement mechanisms as well as a detailed database for future sneeze and speech computational fluid dynamics simulations.
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Affiliation(s)
- Mengtao Han
- School of Architecture and Urban Planning, Huazhong University of Science and Technology, Wuhan, China
| | - Ryozo Ooka
- Institute of Industrial Science, The University of Tokyo, Tokyo, Japan
| | - Hideki Kikumoto
- Institute of Industrial Science, The University of Tokyo, Tokyo, Japan
| | - Wonseok Oh
- Institute of Industrial Science, The University of Tokyo, Tokyo, Japan
| | - Yunchen Bu
- School of Engineering, The University of Tokyo, Tokyo, Japan
| | - Shuyuan Hu
- School of Engineering, The University of Tokyo, Tokyo, Japan
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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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