Poor ventilation worsens short-range airborne transmission of respiratory infection
Open accessAbstract
To explain the observed phenomenon that most SARS-CoV-2 transmission occurs indoors whereas its outdoor transmission is rare, a simple macroscopic aerosol balance model is developed to link short- and long-range airborne transmission. The model considers the involvement of exhaled droplets with initial diameter ≤50 µm in the short-range airborne route, whereas only a fraction of these droplets with an initial diameter within 15 µm or equivalently a final diameter within 5 µm considered in the long-range airborne route. One surprising finding is that the room ventilation rate significantly affects the short-range airborne route, in contrast to traditional belief. When the ventilation rate in a room is insufficient, the airborne infection risks due to both short- and long-range transmission are high. A ventilation rate of 10 L/s per person provides a similar concentration vs distance decay profile to that in outdoor settings, which provides additional justification for the widely adopted ventilation standard of 10 L/s per person. The newly obtained data do not support the basic assumption in the existing ventilation standard ASHRAE 62.1 (2019) that the required people outdoor air rate is constant if the standard is used directly for respiratory infection control. Instead, it is necessary to increase the ventilation rate when the physical distance between people is less than approximately 2 m.
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- Authors
- Li, Y., Cheng, P., & Jia, W.
- Affiliations
- University of Hong Kong (HK)
- Corresponding author
- Li, Yuguo
- Venue
- Indoor Air
- Publisher
- Wiley
- Published
- 2021-10-27
- Volume
- 32
- Issue
- 1
- Pages
- e12946-e12946
- ISSN
- 0905-6947 (ISSN-L)
- 1600-0668
- PMC
- PMC8652937
- OpenAlex
- W3208868503
- Cited by
- 110
- References
- 33
- Citations by year
- 2026: 12 · 2025: 27 · 2024: 21 · 2023: 24 · 2022: 26
- FWCI
- 11.47
- Type
- journal article
- Language
- en
- Open access
- green
- www.ncbi.nlm.nih.gov
- Licence
- Locations
- Indoor Air (publishedVersion)
- PubMed Central (publishedVersion)
- PubMed (publishedVersion)
- The HKU Scholars Hub (University of Hong Kong) (submittedVersion)
- Funders
- Research Grants Council, University Grants Committee
- Topics
- Health Sciences › Medicine › Pulmonary and Respiratory Medicine › Infection Control and Ventilation
- Physical Sciences › Environmental Science › Health, Toxicology and Mutagenesis › Indoor Air Quality and Microbial Exposure
- Physical Sciences › Environmental Science › Global and Planetary Change › COVID-19 impact on air quality
- Keywords
- SARS-CoV-2 transmission, airborne transmission, long-range transmission, exhaled droplets, droplet size, indoor air quality, ventilation standards, respiratory infection control, distance decay
- MeSH terms
- COVID-19, SARS-CoV-2, Aerosols, Air Microbiology, Humans, Respiratory Tract Infections, Ventilation, Air Pollution, Indoor
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