Aerosol Dispersion During Different Phonatory Tasks in Amateur Singers

Abstract Background An issue of concern to the travelling public is the possibility of in-flight transmission of COVID-19 during long- and short-haul flights. The aviation industry maintains that the probability of contracting the illness is small based on reported cases, modelling and data from aerosol dispersion experiments conducted on-board aircraft. Methods Using experimentally derived aerosol dispersion data for a B777–200 aircraft and a modified version of the Wells-Riley equation we estimate inflight infection probability for a range of scenarios involving quanta generation rate and face mask efficiency. Quanta generation rates were selected based on COVID-19 events reported in the literature while mask efficiency was determined from the aerosol dispersion experiments. Results The MID-AFT cabin exhibits the highest infection probability. The calculated maximum individual infection probability (without masks) for a 2-hour flight in this section varies from 4.5% for the ‘Mild Scenario’ to 60.2% for the ‘Severe Scenario’ although the corresponding average infection probability varies from 0.1% to 2.5%. For a 12-hour flight, the corresponding maximum individual infection probability varies from 24.1% to 99.6% and the average infection probability varies from 0.8% to 10.8%. If all passengers wear face masks throughout the 12-hour flight, the average infection probability can be reduced by approximately 73%/32% for high/low efficiency masks. If face masks are worn by all passengers except during a one-hour meal service, the average infection probability is increased by 59%/8% compared to the situation where the mask is not removed. Conclusions This analysis has demonstrated that while there is a significant reduction in aerosol concentration due to the nature of the cabin ventilation and filtration system, this does not necessarily mean that there is a low probability or risk of in-flight infection. However, mask wearing, particularly high-efficiency ones, significantly reduces this risk.

Download Full-text

Assessment of Spray and Pool Scrubbing Efficiencies for Means of Mitigation Against Aerosol Dispersion in the Context of Fuel Debris Retrieval at Fukushima Daiichi: Part I

Journal of Nuclear Engineering and Radiation Science ◽

10.1115/1.4051611 ◽

2021 ◽

Author(s):

Emmanuel Porcheron ◽

Yohan LEBLOIS ◽

Thomas Gélain ◽

Christophe CHAGNOT ◽

Christophe Journeau ◽

...

Keyword(s):

Laser Cutting ◽

Two Phase Flow ◽

Relevant Information ◽

General Context ◽

Phase Flow ◽

Key Factors ◽

Two Phase ◽

Physical Mechanisms ◽

Fukushima Daiichi ◽

Aerosol Dispersion

Abstract The general context of this paper is an evaluation of strategies that can be used to mitigate aerosol dispersion during fuel debris or corium retrieval in damaged Fukushima Daiichi reactors. Knowledge of the aerosol source terms released during fuel debris retrieval operations is one of the key factors for assessing aerosol dispersion leading to the potential dissemination of radionuclides into the environment. Our approach is to couple experimental results from integral tests obtained during laser cutting experiments, analytical tests performed in a dedicated facility to reproduce two-phase flow such as flows representative of pool scrubbing and spray scrubbing conditions, and numerical simulations. Integral tests provide relevant information on the airborne particle release fraction during laser cutting for underwater conditions at different water depths, such as the particle concentration and particle size distribution. However, the detailed characterization of two-phase flows, such as the size and velocity of gas bubble and water droplets, is not possible during laser cutting integral tests. Therefore, a more analytical approach is necessary to obtain detailed information on two-phase flow, composed of bubbles in water, inducing pool scrubbing phenomenon, and droplets in gas generated by spray scrubbing systems, which are essential to the physical mechanisms of both processes and enable their respective efficiencies to be evaluated. The main objectives of this work were to develop models and ensure their validation based on experimental approach for predicting the pool scrubbing and spray scrubbing efficiencies in the context of fuel debris removal at Fukushima Daiichi.

Download Full-text

Effect of gravity on aerosol dispersion and deposition in the human lung after periods of breath holding

Journal of Applied Physiology ◽

10.1152/jappl.2000.89.5.1787 ◽

2000 ◽

Vol 89 (5) ◽

pp. 1787-1792 ◽

Cited By ~ 21

Author(s):

Chantal Darquenne ◽

Manuel Paiva ◽

G. Kim Prisk

Keyword(s):

Flow Rate ◽

Turbulent Mixing ◽

Direct Evidence ◽

Human Lung ◽

Hold Time ◽

Aerosol Deposition ◽

Breath Holding ◽

Breath Hold ◽

Constant Flow Rate ◽

Aerosol Dispersion

To determine the extent of the role that gravity plays in dispersion and deposition during breath holds, we performed aerosol bolus inhalations of 1-μm-diameter particles followed by breath holds of various lengths on four subjects on the ground (1G) and during short periods of microgravity (μG). Boluses of ∼70 ml were inhaled to penetration volumes (Vp) of 150 and 500 ml, at a constant flow rate of ∼0.45 l/s. Aerosol concentration and flow rate were continuously measured at the mouth. Aerosol deposition and dispersion were calculated from these data. Deposition was independent of breath-hold time at both Vp in μG, whereas, in 1G, deposition increased with increasing breath hold time. At Vp = 150 ml, dispersion was similar at both gravity levels and increased with breath hold time. At Vp = 500 ml, dispersion in 1G was always significantly higher than in μG. The data provide direct evidence that gravitational sedimentation is the main mechanism of deposition and dispersion during breath holds. The data also suggest that cardiogenic mixing and turbulent mixing contribute to deposition and dispersion at shallow Vp.

Download Full-text

Aerosol transport measurements and assessment of risk from infectious aerosols: a case study of two German cash-and-carry hardware/DIY stores

10.1101/2021.05.21.21257577 ◽

2021 ◽

Author(s):

eberhard Bodenschatz ◽

Gholamhossein Bagheri ◽

Bardia Hejazi ◽

Birte Thiede ◽

Oliver Schlenczek

Keyword(s):

Upper Bound ◽

Disease Transmission ◽

Face Mask ◽

Indoor Environments ◽

Aerosol Dynamics ◽

Direct Exposure ◽

Decay Times ◽

Dominant Feature ◽

Aerosol Dispersion ◽

Cash And Carry

We report experimental results on aerosol dispersion in two large German cash-and-carry hardware/DIY stores to better understand the factors contributing to disease transmission by infectious human aerosols in large indoor environments. We examined the transport of aerosols similar in size to human respiratory aerosols (0.3μm-10μm) in representative locations, such as high-traffic areas and restrooms. In restrooms, the observed decay of aerosol concentrations was consistent with well-mixed air exchange. In all other locations, fast decay times were measured, which were found to be independent of aerosol size (typically a few minutes). From this, we conclude that in the main retail areas, including at checkouts, rapid turbulent mixing and advection is the dominant feature in aerosol dynamics. With this, the upper bound of risk for airborne disease transmission to a susceptible is determined by direct exposure to the exhalation cloud of an infectious. For the example of the SARS-CoV-2 virus, we find when speaking without a face mask and aerosol sizes up to an exhalation (wet) diameter of 50μm, a distance of 1.5me to be unsafe. However, at the smallest distance between an infectious and a susceptible, while wearing typical surgical masks and for all sizes of exhaled aerosol, the upper bound of infection risk is only ∼ 5% and decreases further by a factor of 100 (∼ 0.05%) for typical FFP2 masks for a duration of 20 min. This upper bound is very conservative and we expect the actual risk for typical encounters to be much lower. The risks found here are comparable to what might be expected in calm outdoor weather.

Download Full-text