Review of experimental measurements on particle size distribution and airflow behaviors during human respiration

Hu, Nan; Yuan, Feng; Gram, Annika; Yao, Runming; Sadrizadeh, Sasan

doi:10.1016/j.buildenv.2023.110994

Cited by 4 publications

(1 citation statement)

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“…Another study used both APS and light scattering video observations of the respiratory aerosol, finding particle counts consistent with prior APS measurements but also observing impressive clouds of particles that appeared to contain numerous aerosols much larger than observed by their APS [29]. However, precise measurements of the sizes and trajectories of ejected particles from high-speed video are limited by their often rather narrow field of view and remain restricted to technologically highly advanced laboratories [30][31][32][33][34].…”

Section: Introductionmentioning

confidence: 66%

Resolving the Loss of Intermediate-Size Speech Aerosols in Funnel-Guided Particle Counting Measurements

Kakeshpour,

Bax

2024

Atmosphere

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Modeling of airborne virus transmission and protection against it requires knowledge of the amount of biofluid emitted into the atmosphere and its viral load. Whereas viral concentrations in biofluids are readily measured by quantitative PCR, the total volume of fluids aerosolized during speaking, as measured by different researchers using various technologies, differs by several orders of magnitude. We compared collection methods in which the aerosols first enter into a low-humidity chamber either by direct injection or via commonly used funnel and tubing arrangements, followed by standard optical particle sizer measurement. This “collect first, measure later” approach sacrifices the recording of the temporal correlation between aerosol generation and sound types such as plosives and vowels. However, the direct-injection mode prevents inertia deposition associated with the funnel arrangements and reveals far more intermediate-size (5–20 μm in diameter) particles that can dominate the total mass of ejected respiratory aerosol. The larger aerosol mass observed with our method partially reconciles the large discrepancy between the SARS-CoV-2 infectious dose estimated from superspreader event analyses and that from human challenge data. Our results also impact measures to combat airborne virus transmission because they indicate that aerosols that settle faster than good room ventilation rates can dominate this process.

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