Inhalation of expiratory droplets in aircraft cabin

National Air Transportation Center of Excellence for Research in the Intermodal Transport Environment (RITE), School of Mechanical Engineering, Purdue University, West Lafayette, IN, USA.
Indoor Air (Impact Factor: 4.9). 08/2011; 21(4):341-50. DOI: 10.1111/j.1600-0668.2011.00709.x
Source: PubMed


Abstract Airliner cabins have high occupant density and long exposure time, so the risk of airborne infection transmission could be high if one or more passengers are infected with an airborne infectious disease. The droplets exhaled by an infected passenger may contain infectious agents. This study developed a method to predict the amount of expiratory droplets inhaled by the passengers in an airliner cabin for any flight duration. The spatial and temporal distribution of expiratory droplets for the first 3 min after the exhalation from the index passenger was obtained using the computational fluid dynamics simulations. The perfectly mixed model was used for beyond 3 min after the exhalation. For multiple exhalations, the droplet concentration in a zone can be obtained by adding the droplet concentrations for all the exhalations until the current time with a time shift via the superposition method. These methods were used to determine the amount of droplets inhaled by the susceptible passengers over a 4-h flight under three common scenarios. The method, if coupled with information on the viability and the amount of infectious agent in the droplet, can aid in evaluating the infection risk.
The distribution of the infectious agents contained in the expiratory droplets of an infected occupant in an indoor environment is transient and non-uniform. The risk of infection can thus vary with time and space. The investigations developed methods to predict the spatial and temporal distribution of expiratory droplets, and the inhalation of these droplets in an aircraft cabin. The methods can be used in other indoor environments to assess the relative risk of infection in different zones, and suitable measures to control the spread of infection can be adopted. Appropriate treatment can be implemented for the zone identified as high-risk zones.

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    • "Possou et al. [16] and Muzumdar et al. [17] used validated CFD and a small-scale water model to assess the impact of scaling and body movement on contaminant transport in airliner cabins. Gupta et al. [18] [19] developed a method to predict the amount of expiratory droplets inhaled by the passengers in an airliner cabin for any flight duration; the method was used to determine the amount of droplets inhaled by the susceptible passengers over a 4-h flight, under three common scenarios. They also computed the transport of the droplets exhaled by the index patient seated in the middle of a seven-row, twin-aisle, fully-occupied cabin using CFD simulations . "
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    ABSTRACT: Nowadays the achievement of a comfortable environment in aircraft cabins is a factor of paramount importance in air travel business competition; on the other hand, the need of reducing the propulsion fuel cost has driven the airline companies to adopt air handling systems that may reduce the levels of thermal comfort and air quality inside the cabins of commercial airliners. With the aim of contributing to a better knowledge of this matter, this paper reports the results of an experimental study upon the indoor air quality aboard commercial aircrafts for 14 domestic flights less than 1 h and half long. The parameters monitored were temperature, relative humidity and carbon dioxide concentration; the measurements were performed during the whole flight from the take-off to the landing.The relative humidity inside the cabin was also calculated using the rates of outside air and the carbon dioxide as a ventilation tracer; the theoretical results were compared with the measured data. The relationship between relative humidity and carbon dioxide concentration during fights was highlighted in order to define the environmental conditions that may provide acceptable levels of both the air quality and hygrometric comfort to the crew and passengers. The results of calculations confirmed the possibility of improving the hygrometric conditions in aircraft cabins without the need of using humidification systems.
    Building and Environment 09/2013; 67:69–81. DOI:10.1016/j.buildenv.2013.05.006 · 3.34 Impact Factor
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    • "Relatively few studies have focused on breathing airflow dynamics. Gupta and colleagues performed a series of experiments to characterise the morphology and flow dynamics of nasal and mouth breathing [21], and followed this by computer simulations of how such breath plumes might disseminate and be inhaled in a fully occupied aircraft cabin [22], [23]. Tang et al. [17] used a real-time, non-invasive, shadowgraph method to visualise the airflows produced during nasal and mouth breathing, talking (counting), coughing, laughing and sneezing healthy volunteers, though this was only a qualitative visualisation study without any quantitative assessment being attempted. "
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    ABSTRACT: Natural human exhalation flows such as coughing, sneezing and breathing can be considered as 'jet-like' airflows in the sense that they are produced from a single source in a single exhalation effort, with a relatively symmetrical, conical geometry. Although coughing and sneezing have garnered much attention as potential, explosive sources of infectious aerosols, these are relatively rare events during daily life, whereas breathing is necessary for life and is performed continuously. Real-time shadowgraph imaging was used to visualise and capture high-speed images of healthy volunteers sneezing and breathing (through the nose - nasally, and through the mouth - orally). Six volunteers, who were able to respond to the pepper sneeze stimulus, were recruited for the sneezing experiments (2 women: 27.5±6.36 years; 4 men: 29.25±10.53 years). The maximum visible distance over which the sneeze plumes (or puffs) travelled was 0.6 m, the maximum sneeze velocity derived from these measured distances was 4.5 m/s. The maximum 2-dimensional (2-D) area of dissemination of these sneezes was 0.2 m(2). The corresponding derived parameter, the maximum 2-D area expansion rate of these sneezes was 2 m(2)/s. For nasal breathing, the maximum propagation distance and derived velocity were 0.6 m and 1.4 m/s, respectively. The maximum 2-D area of dissemination and derived expansion rate were 0.11 m(2) and 0.16 m(2)/s, respectively. Similarly, for mouth breathing, the maximum propagation distance and derived velocity were 0.8 m and 1.3 m/s, respectively. The maximum 2-D area of dissemination and derived expansion rate were 0.18 m(2) and 0.17 m(2)/s, respectively. Surprisingly, a comparison of the maximum exit velocities of sneezing reported here with those obtained from coughing (published previously) demonstrated that they are relatively similar, and not extremely high. This is in contrast with some earlier estimates of sneeze velocities, and some reasons for this difference are discussed.
    PLoS ONE 04/2013; 8(4):e59970. DOI:10.1371/journal.pone.0059970 · 3.23 Impact Factor
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    • "Quanta is a term defined by Wells, 1955 that indicates that if a person inhales one quanta, the probability of his getting infected is 1-1/e. Any of these quantities can be used to define the amount of dose exhaled, then the dose inhaled can be calculated using equation (1) (Gupta et al., 2011b "
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    ABSTRACT: Abstract  Passengers in an aircraft cabin can have different risks of infection from airborne infectious diseases such as influenza, severe acute respiratory syndrome (SARS), and tuberculosis (TB) because of the non-uniform airflow in an aircraft cabin. The current investigation presents a comprehensive approach to assessing the spatial and temporal distributions of airborne infection risk in an aircraft cabin. A case of influenza outbreak was evaluated in a 4-h flight in a twin-aisle, fully occupied aircraft cabin with the index passenger seated at the center of the cabin. The approach considered the characteristics of the exhalation of the droplets carrying infectious agents from the index passenger, the dispersion of these droplets, and the inhalation of the droplets by susceptible passengers. Deterministic and probabilistic approaches were used to quantify the risks based on the amount of inhaled influenza virus RNA particles and quanta, respectively. The probabilistic approach indicated that the number of secondary infection cases can be reduced from 3 to 0 and 20 to 11, for influenza cases if N95 respirator masks are used by the passengers. The approach and methods developed can easily be implemented in other enclosed spaces such as buildings, trains, and buses to assess the infection risk. PRACTICAL IMPLICATIONS: Airborne infectious disease transmission could take place in enclosed environments such as buildings and transport vehicles. The infection risk is difficult to estimate, and very few mitigation methods are available. This study used a 4-h flight as an example in analyzing the infection risk from influenza and in mitigating the risk with an N95 mask. The results will be useful to the airline industry in providing necessary protection to passengers and crew, and the results can also be used for other enclosed spaces.
    Indoor Air 02/2012; 22(5):388-95. DOI:10.1111/j.1600-0668.2012.00773.x · 4.90 Impact Factor
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