Special Issue on COVID-19 Aerosol Drivers, Impacts and Mitigation (XVI)

Wenzhu Duan1,2, Dan Mei This email address is being protected from spambots. You need JavaScript enabled to view it.1,2, Jiaqian Li1, Zihan Liu1, Mengfan Jia1, Shanshan Hou2

1 Hubei Key Laboratory for Efficient Utilization and Agglomeration of Metallurgic Mineral Resources, Wuhan University of Science and Technology, Wuhan 430081, China
2 Hubei Provincial Industrial Safety Engineering Technology Research Center, Wuhan University of Science and Technology, Wuhan 430081, China

Received: July 31, 2020
Revised: April 7, 2021
Accepted: April 14, 2021

 Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.

Download Citation: ||https://doi.org/10.4209/aaqr.200478  

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Cite this article:

Duan, W., Mei, D., Li, J., Liu, Z., Ja, M., Hou, S. (2021). Spatial Distribution of Exhalation Droplets in the Bus in Different Seasons. Aerosol Air Qual. Res. 21, 200478. https://doi.org/10.4209/aaqr.200478


  • Four seasons (T = 278 K/288 K/298 K/308 K) and four exhalation positions are considered.
  • The higher the temperature, the lower the droplets diffusion speed.
  • In summer, the time required for droplets to reach the driver is 25% delayed compared to winter.
  • Strengthening the isolation of upper space of the driver can reduce the driver's risk of infection.
  • Low-risk area and high-risk area could be concluded from droplet spatial distribution.


In closed buses, the spread of droplets with viruses/bacteria may cause the spread of respiratory infectious diseases. Discrete phase modeling is used to simulate the diffusion characteristics and concentration distribution of droplets at different temperatures and different exhalation positions by ANSYS FLUENT software. The integral concentration of droplets at different locations can be quantified, which leads to identification of low-risk areas and high-risk areas in the bus.

Results show that a higher outdoor temperature leads to lower droplets’ diffusion speed and longer time until the droplets reach the driver. In addition, based on the integral concentration of droplets at the seats, regardless of whether a passenger exhales droplets in the front row of the bus, the position of the rear door or the last row of the bus, the seats in the last row of the bus away from the door belong to the low-risk area. In contrast, the seats near the door and the middle seat in the bus are higher risk areas. Consequently, this study proposed sitting on a seat in the low-risk area as a means to reduce the risk of passengers. Moreover, safety protection facilities around the driver should be modified to improve the isolation of the upper area of the driver’s location, so as to effectively prevent the droplet diffusion towards the driver, thereby effectively reducing the driver’s risk of infection.

Keywords: Expiratory droplets, Droplet diffusion, Concentration distribution, Outdoor temperature

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