Special Issue on Air Quality in a Changed World: Regional, Ambient, and Indoor Air Concentrations from the COVID to Post-COVID Era

Damian E. Ramajo This email address is being protected from spambots. You need JavaScript enabled to view it., Santiago Corzo 

Research Center for Computing Methods, CONICET – University National of Litoral, Route 168 – CCT Litoral - Santa Fe 3000, Argentina

Received: December 13, 2021
Revised: May 10, 2022
Accepted: June 3, 2022

 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.210334  

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Cite this article:

Ramajo, D.E., Corzo, S. (2022). Airborne Transmission Risk in Urban Buses: A Computational Fluid Dynamics Study. Aerosol Air Qual. Res. https://doi.org/10.4209/aaqr.210334


  • The droplets released during sneezing can travel more than 3 m before deposit.
  • The HVAC system only can capture droplets small than 5 µm.
  • The average transmission risk by aerosols reduces to a half if the air is renew 10 times an hour.


The Heat, Ventilation, Air Conditioning (HVAC) systems in urban buses promote high particle motion. In this paper the effect of centralized roof-top HVAC on virus transmission by droplets caused by sneezing and coughing was studied with the Lagrangian approach while the transmission through aerosols caused by breathing and talking was modeled with the Eulerian tracer method. It was found that the large droplets (> 200 μm) can travel more than 3 m without being affected by the airflow. On the other hand, the small droplets (< 5 μm) are easily dragged, dispersed, and also captured by the HVAC. On the other hand, aerosols are quickly spread by the HVAC. It was found that the centralized roof-top HVAC reduces the concentration in the central zone, but it is ineffective to renew the air in the front and rear sides. The Wells-Riley risk model showed that the average risk across the whole bus can be reduced to a half and a quarter by renewing the air of the cabin 10 times per hour.

Keywords: CFD, Lagrangian and Eulerian simulation, Droplets, Virus transmission, Urban bus

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