Reducing Virus Transmission from Heating, Ventilation, and Air Conditioning Systems of Urban Subways

Ata Nazari, Jiarong Hong, Farzad Taghizadeh-Hesary, Farhad Taghizadeh-Hesary

Research output: Contribution to journalArticlepeer-review


Aerosols carrying the virus inside enclosed spaces is an important mode of transmission for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), as supported by growing evidence. Urban subways are one of the most frequented enclosed spaces. The subway is a utilitarian and low-cost transit system in modern society. However, studies are yet to demonstrate patterns of viral transmission in subway heating, ventilation, and air conditioning (HVAC) systems. To fill this gap, we performed a computational investigation of the airflow (and associated aerosol transmission) in an urban subway cabin equipped with an HVAC system. We employed a transport equation for aerosol concentration, which was added to the basic buoyant solver to resolve the aerosol transmission inside the subway cabin. This was achieved by considering the thermal, turbulent, and induced ventilation flow effects. Using the probability of encountering aerosols on sampling surfaces crossing the passenger breathing zones, we detected the highest infection risk zones inside the urban subway under different settings. We proposed a novel HVAC system that can impede aerosol spread, both vertically and horizontally, inside the cabin. In the conventional model, the maximum probability of encountering aerosols from the breathing of infected individuals near the fresh-air ducts was equal to 51.2%. This decreased to 3.5% in the proposed HVAC model. Overall, using the proposed HVAC system for urban subways led to a decrease in the mean value of the probability of encountering the aerosol by approximately 84% compared with that of the conventional system.

Original languageEnglish (US)
Article number796
Issue number12
StatePublished - Dec 2022

Bibliographical note

Funding Information:
This research was financially supported by the Grant-in-Aid for the Excellent Young Researcher of the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT) and Grant-in-Aid for Young Scientists (No. 22K13432) of the Japan Society for the Promotion of Science (JSPS).

Publisher Copyright:
© 2022 by the authors.


  • aerosol
  • air circulation
  • indoor air quality
  • OpenFOAM
  • SARS-CoV-2
  • urban subway
  • ventilation

PubMed: MeSH publication types

  • Journal Article


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