Protected zone ventilation and reduced personal exposure to airborne cross-infection

Cao, Guangyu; Nielsen, Peter; Jensen, Rasmus Lund; Heiselberg, Per; Liu, Li; Heikkinen, Jorma

doi:10.1111/ina.12142

Cited by 72 publications

(45 citation statements)

References 19 publications

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“…This 2‐stage exposure might be especially worthy of separate investigation when evaluating the performance of some control measures, such as face masks and PV. Evidently, these control measures can effectively avoid the high‐concentration direct exposure, but the secondary indirect exposure may still be sufficient to cause infection . In general, to understand the whole transmission process and the role of direct and indirect transmissions, transient studies will be required.…”

Section: Discussion and Future Perspectivesmentioning

confidence: 99%

Airborne spread of expiratory droplet nuclei between the occupants of indoor environments: A review

2018

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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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Section: Discussion and Future Perspectivesmentioning

confidence: 99%

Airborne spread of expiratory droplet nuclei between the occupants of indoor environments: A review

2018

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“…Highlights  Droplet evaporation and transport(initial size 10μm/50μm) in bus are studied by CFD. Since the outbreak of SARS in 2003, there have been an abundance of experimental and/or numerical studies on indoor ventilation and airborne transmission in inter-units of buildings [3,7,8], hospital isolation rooms [9][10][11][12][13][14][15][16][17][18] or operating rooms [19], general indoor environments [20,21]. Besides for vehicle indoor environments, a number of studies emphasized indoor transmission in airplane cabins [22][23][24][25] and high-speed train [26].…”

Section: Graphical Abstractmentioning

confidence: 99%

Transmission of pathogen-laden expiratory droplets in a coach bus

Xia

Yang

et al. 2020

Journal of Hazardous Materials

159

108

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J o u r n a l P r e -p r o o f  RH=95% induces less droplets suspended in air and more deposition fraction(85%-100%). Wet air, sitting at nonadjacent seats, supply to bus backward reduce infection risk. AbstractDroplet dispersion carrying viruses/bacteria in enclosed/crowded buses may induce transmissions of respiratory infectious diseases, but the influencing mechanisms have been rarely investigated. By conducting high-resolution CFD simulations, this paper investigates the evaporation and transport of solid-liquid mixed droplets (initial diameter 10μm and 50μm, solid to liquid ratio is 1:9) exhaled in a coach bus with 14 thermal manikins. Five air-conditioning supply directions and ambient relative humidity (RH=35% and 95%) are considered. Results show that ventilation effectiveness, RH and initial droplet size significantly influence droplet transmissions in coach bus. 50μm droplets tend to evaporate completely within 1.8s and 7s as RH=35% and 95% respectively, while 0.2s or less for 10μm droplets. Thus 10μm droplets diffuse farther with wider range than 50μm droplets which tend to deposit more on surfaces. Droplet dispersion pattern differs due to various interactions of gravity, ventilation flows and the upward thermal body plume. The fractions of droplets suspended in air, deposited on wall surfaces are quantified. This study implies high RH, backward supply direction and passengers sitting at nonadjacent seats can effectively reduce infection risk of droplet transmission in buses. Besides taking masks, regular cleaning is also recommended since 85%-100% of droplets deposit on object surfaces.J o u r n a l P r e -p r o o f

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“…For example, Chen et al (2010) investigated the droplets/particles cross transmission between dental healthcare workers and patient. Cao et al (2015) examined the performance of protected zone ventilation and hybrid protected zone ventilation in reducing person to person airborne cross transmission in office room by experiment. Habchi et al (2014) studied the cross-infection between occupants in the room with a mathematical multi-plume multi-layer transport model.…”

Section: Introductionmentioning

confidence: 99%

Person to person droplets transmission characteristics in unidirectional ventilated protective isolation room: The impact of initial droplet size

Yang

Zhao

2016

Build. Simul.

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Person to person droplets/particles or contaminant cross transmission is an important issue in ventilated environment, especially in the unidirectional ventilated protective isolation room (UVPIR) where the patient's immune system is extremely low and easily infected. We simulated the dispersion process of the droplets with initial diameter of 100 μm, 10 μm and gaseous contaminant in unidirectional ventilated protective isolation room and studied the droplets dispersion and cross transmission with different sizes. The droplets with initial size of 100 μm settle out of the coughing jet quickly after coming out from mouth and cannot be carried by the coughing jet to the human thermal plume affecting (HTPA) zone of the susceptible manikin. Hence, the larger droplets disperse mainly in the HTPA zone of the source manikin, and the droplets cross transmission between source manikin and susceptible manikin is very small. The droplets with initial size of 10 μm and gaseous contaminant have similar dispersion but different removal process in the UVPIR. Part of the droplets with initial size of 10 μm and gaseous contaminant that are carried by the higher velocity coughing airflow can enter the HTPA zone of the susceptible manikin and disperse around it. The other part cannot spread to the susceptible manikin's HTPA zone and mainly spread in the source manikin's HTPA zone. The results from this study would be useful for UVPIR usage and operation in order to minimize the risk of cross infection.

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Protected zone ventilation and reduced personal exposure to airborne cross-infection

Cited by 72 publications

References 19 publications

Airborne spread of expiratory droplet nuclei between the occupants of indoor environments: A review

Airborne spread of expiratory droplet nuclei between the occupants of indoor environments: A review

Transmission of pathogen-laden expiratory droplets in a coach bus

Person to person droplets transmission characteristics in unidirectional ventilated protective isolation room: The impact of initial droplet size

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