Modality of human expired aerosol size distributions

Johnson, Graham R.; Morawska, Lidia; Ristovski, Zoran; Hargreaves, Megan; Mengersen, Kerrie; Chao, Christopher Yu Hang; Wan, Man Pun; Li, Y.; Xie, Xaiojan; Katoshevski, David; Corbett, Stephen

doi:10.1016/j.jaerosci.2011.07.009

Cited by 574 publications

(887 citation statements)

References 26 publications

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“…One study indicated that the majority of the cough aerosol was contained in the initial part of a cough (Day et al 2010), and this is consistent with theories about the sites of origin of aerosol particles in the respiratory tract Johnson et al 2011). One initial idea for our cough simulator involved simply spraying the aerosol into the cough air as it was being coughed out.…”

Section: Discussionsupporting

confidence: 58%

A Cough Aerosol Simulator for the Study of Disease Transmission by Human Cough-Generated Aerosols

Lindsley

Reynolds

Szalajda

et al. 2013

Aerosol Science and Technology

118

143

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Aerosol particles expelled during human coughs are a potential pathway for infectious disease transmission. However, the importance of airborne transmission is unclear for many diseases. To better understand the role of cough aerosol particles in the spread of disease and the efficacy of different types of protective measures, we constructed a cough aerosol simulator that produces a humanlike cough in a controlled environment. The simulated cough has a 4.2 l volume and is based on coughs recorded from influenza patients. In one configuration, the simulator produces a cough aerosol containing particles from 0.1 to 100 µm in diameter with a volume median diameter (VMD) of 8.5 µm and a geometric standard deviation (GSD) of 2.9. In a second configuration, the cough aerosol has a size range of 0.1-30 µm, a VMD of 3.4 µm, and a GSD of 2.3. The total aerosol volume expelled during each cough is 68 µl. By generating a controlled and reproducible artificial cough, the simulator allows us to test different ventilation, disinfection, and personal protection scenarios. The system can be used with live pathogens, including influenza virus, which allows isolation precautions used in the healthcare field to be tested without risk of exposure for workers or patients. The information gained from tests with the simulator will help to better understand the transmission of infectious diseases, develop improved techniques for infection control, and improve safety for healthcare workers and patients.

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Section: Discussionsupporting

confidence: 58%

A Cough Aerosol Simulator for the Study of Disease Transmission by Human Cough-Generated Aerosols

Lindsley

Reynolds

Szalajda

et al. 2013

Aerosol Science and Technology

118

143

View full text Add to dashboard Cite

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“…10 5 (Duguid 1946), or even less, e.g. 10 7 (Johnson et al 2011). The low volume fraction (⌧1 %) allows us to neglect the modifications to the droplet speeds required at higher particle concentration .…”

Section: Theoretical Modelmentioning

confidence: 99%

“…Duguid 1946), with recent focus on the improvement of the precision of measurement of the small submicrometre range (e.g. Morawska 2006;Johnson et al 2011;Zayas et al 2012). An example of droplet size distribution for coughs is shown in figure 17, which indicates a peak drop size of ⇠15 µm, the associated settling speed being 6.5 mm s 1 in ambient air typical of winter indoor conditions.…”

mentioning

confidence: 99%

Violent expiratory events: on coughing and sneezing

2014

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Violent respiratory events such as coughs and sneezes play a key role in transferring respiratory diseases between infectious and susceptible individuals. We present the results of a combined experimental and theoretical investigation of the fluid dynamics of such violent expiratory events. Direct observation of sneezing and coughing events reveals that such flows are multiphase turbulent buoyant clouds with suspended droplets of various sizes. Our observations guide the development of an accompanying theoretical model of pathogen-bearing droplets interacting with a turbulent buoyant momentum puff. We develop in turn discrete and continuous models of droplet fallout from the cloud in order to predict the range of pathogens. According to the discrete fallout model droplets remain suspended in the cloud until their settling speed matches that of the decelerating cloud. A continuous fallout model is developed by adapting models of sedimentation from turbulent fluids. The predictions of our theoretical models are tested against data gathered from a series of analogue experiments in which a particle-laden cloud is ejected into a relatively dense ambient. Our study highlights the importance of the multiphase nature of respiratory clouds, specifically the suspension of the smallest drops by circulation within the cloud, in extending the range of respiratory pathogens.

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“…Studies of aerosols generated by cough and sneeze have been shown to include particles that vary over several orders of magnitude [14][15][16][17][18] and contain pathogens. [19][20][21][22] Figure 1(a) illustrates an aerosol plume, such as might be emitted by a cough.…”

Section: Aerosol Transmissionmentioning

confidence: 99%