Document Type : Regular Article


Chemical Engineering Department, Hamedan University of Technology, P. O. Box: 65155, Hamedan, Iran


The size and lifetime of evaporating sneeze droplets in the indoor environment were studied experimentally and theoretically. The effects of indoor temperature Tand indoor humidity RHon evaporating droplets with the initial diameters of 4.9, 8.1, 17.2, and 29.7 μm were investigated. The size distribution and mean size of droplets were obtained by a laser particle sizer. The experimental data showed that the possibility of aerosolized droplets increased from 25.5 to 36.1 % by increasing Tfrom 18 to 30 °C and decreased from 36.1 to 13.6 % by increasing RH from 30 to 60 %. A one-dimensional droplet evaporation model was used to estimate the lifetime of the droplet. A critical RH of 40 % was found; above it, the lifetime of the droplet exponentially increases. The effect of the initial diameter of droplets was higher than that of RH and also the impact of RH was higher than that of Ton the lifetime of the aerosolized droplet nuclei. A significant effect of environmental conditions on the lifetime of the droplet was found over the range of 26 °C ≤ T ≤ 30 °C and RH ≤ 40 %, while the effect decreased in the range of 18 °C ≤ T ≤ 22 °C and RH > 40 %, where a minimal shrinkage of droplets took place because of the hygroscopic growth of droplets. The results of this study do not imply that the COVID-19 virus will be deactivated at the end of the lifetime of the droplet, but it represents that controlling the indoor environment is important for droplets to carry the virus.


Main Subjects

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