Journal ArticleDOI
How far droplets can move in indoor environments--revisiting the Wells evaporation-falling curve.
Reads0
Chats0
TLDR
The results indicate that a droplet's size predominately dictates its evaporation and movement after being expelled, and there is a need to examine the air distribution systems in hospital wards for controlling both airborne and droplet-borne transmitted diseases.Abstract:
UNLABELLED A large number of infectious diseases are believed to be transmitted between people via large droplets and by airborne routes. An understanding of evaporation and dispersion of droplets and droplet nuclei is not only significant for developing effective engineering control methods for infectious diseases but also for exploring the basic transmission mechanisms of the infectious diseases. How far droplets can move is related to how far droplet-borne diseases can transmit. A simple physical model is developed and used here to investigate the evaporation and movement of droplets expelled during respiratory activities; in particular, the well-known Wells evaporation-falling curve of droplets is revisited considering the effect of relative humidity, air speed, and respiratory jets. Our simple model considers the movement of exhaled air, as well as the evaporation and movement of a single droplet. Exhaled air is treated as a steady-state non-isothermal (warm) jet horizontally issuing into stagnant surrounding air. A droplet is assumed to evaporate and move in this non-isothermal jet. Calculations are performed for both pure water droplets and droplets of sodium chloride (physiological saline) solution (0.9% w/v). We calculate the droplet lifetimes and how droplet size changes, as well as how far the droplets travel in different relative humidities. Our results indicate that a droplet's size predominately dictates its evaporation and movement after being expelled. The sizes of the largest droplets that would totally evaporate before falling 2 m away are determined under different conditions. The maximum horizontal distances that droplets can reach during different respiratory activities are also obtained. Our study is useful for developing effective prevention measures for controlling infectious diseases in hospitals and in the community at large. PRACTICAL IMPLICATIONS Our study reveals that for respiratory exhalation flows, the sizes of the largest droplets that would totally evaporate before falling 2 m away are between 60 and 100 microm, and these expelled large droplets are carried more than 6 m away by exhaled air at a velocity of 50 m/s (sneezing), more than 2 m away at a velocity of 10 m/s (coughing) and less than 1 m away at a velocity of 1 m/s (breathing). These findings are useful for developing effective engineering control methods for infectious diseases, and also for exploring the basic transmission mechanisms of the infectious diseases. There is a need to examine the air distribution systems in hospital wards for controlling both airborne and droplet-borne transmitted diseases.read more
Citations
More filters
Journal ArticleDOI
Transmission of COVID-19 virus by droplets and aerosols: A critical review on the unresolved dichotomy.
TL;DR: It is demonstrated that the nosocomial transmission by airborne SARS-CoV-2 viral-laden aerosols in healthcare facilities may be plausible and clearly defined, science-based administrative, clinical, and physical measures are of paramount importance to eradicate the COVID-19 pandemic from the world.
Journal ArticleDOI
It Is Time to Address Airborne Transmission of Coronavirus Disease 2019 (COVID-19).
Lidia Morawska,Donald K. Milton +1 more
TL;DR: The following scientists reviewed the document: Jonathan Abbatt, John Adgate, Alireza Afshari, KangHo Ahn, Francis Allard, Joseph Allen, Celia Alves, Meinrat O.Hussein, Gabriel Isaacman-VanWertz, Jouni J.C.Johansson, Jan Kaczmarczyk, George Kallos, David Katoshevski, Frank Kelly, Soren Kjaergaard,Luke D.
Journal ArticleDOI
A high-resolution human contact network for infectious disease transmission
Marcel Salathé,Maria A. Kazandjieva,Jung Woo Lee,Philip Levis,Marcus W. Feldman,James Holland Jones +5 more
TL;DR: High-resolution data of CPIs during a typical day at an American high school is obtained, permitting the reconstruction of the social network relevant for infectious disease transmission and suggested that contact network data are required to design strategies that are significantly more effective than random immunization.
Journal ArticleDOI
Aerosol emission and superemission during human speech increase with voice loudness
Sima Asadi,Anthony S. Wexler,Christopher D. Cappa,Santiago Barreda,Nicole M. Bouvier,William D. Ristenpart +5 more
TL;DR: It is shown that the rate of particle emission during normal human speech is positively correlated with the loudness (amplitude) of vocalization, and the phenomenon of speech superemission cannot be fully explained either by the phonic structures or the amplitude of the speech.
Journal ArticleDOI
The coronavirus pandemic and aerosols: Does COVID-19 transmit via expiratory particles?
TL;DR: As of late March 2020, the global COVID-19 pandemic caused by the SARS-CoV-2 virus has battered the world and more than 40,000 people have died with over 800,000People confirmed infected.
References
More filters
BookDOI
Multiphase Flows with Droplets and Particles
TL;DR: In this article, the authors present a test case for a single-phase flow Turbulence Modulation by Particles (SPM) model using the Brownian Motion model.
Journal ArticleDOI
Some measurements in the self preserving jet
Israel Wygnanski,H. E. Fiedler +1 more
TL;DR: In this paper, the axisymmetric turbulent incompressible and isothermal jet was investigated by use of linearized constant-temperature hot-wire anemometers and the quantities measured include mean velocity, turbulence stresses, intermittency, skewness and flatness factors, correlations, scales, low-frequency spectra and convection velocity.
Journal ArticleDOI
Evidence of Airborne Transmission of the Severe Acute Respiratory Syndrome Virus
Ignatius Tak-sun Yu,Yuguo Li,Tze Wai Wong,Wilson W.S. Tam,Andy Chan,Joseph H.W. Lee,Dennis Y.C. Leung,Thomas C. Ho +7 more
TL;DR: Airborne spread of the virus appears to explain this large community outbreak of SARS in Hong Kong, and future efforts at prevention and control must take into consideration the potential for airborne spread of this virus.
Journal ArticleDOI
Toward Understanding the Risk of Secondary Airborne Infection: Emission of Respirable Pathogens
TL;DR: Patients termed “superspreaders” or “dangerous disseminators” are those infrequently encountered persons with high values of cough and/or sneeze frequency, elevated pathogen concentration in respiratory fluid, and/ or increased respirable aerosol volume per expiratory event such that their pathogen emission rate is much higher than average.