How can airborne transmission of COVID-19 indoors be minimised?

Lidia Morawska¹, Julian W Tang², William Bahnfleth³, Philomena M Bluyssen⁴, Atze Boerstra⁵, Giorgio Buonanno⁶, Junji Cao⁷, Stephanie Dancer⁸, Andres Floto⁹, Francesco Franchimon¹⁰, Charles Haworth¹¹, Jaap Hogeling¹², Christina Isaxon¹³, Jose L Jimenez¹⁴, Jarek Kurnitski¹⁵, Yuguo Li¹⁶, Marcel Loomans¹⁷, Guy Marks¹⁸, Linsey C Marr¹⁹, Livio Mazzarella²⁰, Arsen Krikor Melikov²¹, Shelly Miller²², Donald K Milton²³, William Nazaroff²⁴, Peter V Nielsen²⁵, Catherine Noakes²⁶, Jordan Peccia²⁷, Xavier Querol²⁸, Chandra Sekhar²⁹, Olli Seppänen³⁰, Shin-Ichi Tanabe³¹, Raymond Tellier³², Kwok Wai Tham²⁹, Pawel Wargocki²¹, Aneta Wierzbicka³³, Maosheng Yao³⁴

Affiliations

¹ International Laboratory for Air Quality and Heath (ILAQH), WHO Collaborating Centre for Air Quality and Health, School of Earth and Atmospheric Sciences, Queensland University of Technology, Brisbane, Queensland, Australia. Electronic address: l.morawska@qut.edu.au.
² Respiratory Sciences, University of Leicester, Leicester, United Kingdom.
³ Department of Architectural Engineering, The Pennsylvania State University, USA.
⁴ Faculty of Architecture and the Built Environment, Delft University of Technology, the Netherlands.
⁵ REHVA (Federation of European Heating, Ventilation and Air Conditioning Associations), BBA Binnenmilieu, the Netherlands.
⁶ Department if Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, Italy.
⁷ Key Lab of Aerosol Chemistry and Physics Chinese Academy of Sciences, Xi'an, Beijing, China.
⁸ Edinburgh Napier University and NHS Lanarkshire, Scotland, United Kingdom.
⁹ Department of Medicine, University of Cambridge, United Kingdom.
¹⁰ Franchimon ICM, the Netherlands.
¹¹ Cambridge Centre for Lung Infection, Royal Papworth Hospital and Department of Medicine, University of Cambridge, Cambridge, United Kingdom.
¹² International Standards at ISSO, ISSO International Project, the Netherlands.
¹³ Ergonomics and Aerosol Technology Lund University, Lund, Sweden.
¹⁴ Department of Chemistry, and Cooperative Institute for Research in Environmental Sciences (CIRES) University of Colorado, Boulder, USA.
¹⁵ REHVA Technology and Research Committee, Tallinn University of Technology, Estonia.
¹⁶ Department of Mechancal Engineering, Hong Kong University, University of Hong Kong, Pokfulam, Hong Kong, China.
¹⁷ Department of the Built Environment, Eindhoven University of Technology (TU/e), the Netherlands.
¹⁸ Centre for Air quality Research and evaluation (CAR), University of New South Wales (UNSW), Sydney, New South Wales, Australia.
¹⁹ Civil and Environmental Engineering, VA Tech, USA.
²⁰ AiCARR, Politecnico di Milano, Italy.
²¹ International Centre for Indoor Environment and Energy, Department of Civil Engineering, Technical University of Denmark, Denmark.
²² Mechanical Engineering, University of Colorado, Boulder, USA.
²³ Environmental Health, School of Public Health, University of Maryland, USA.
²⁴ Department of Civil and Environmental Engineering, University of California, Berkeley, CA, USA.
²⁵ Faculty of Engineering and Science, Department of Civil Engineering, Aalborg University, Denmark.
²⁶ School of Civil Engineering, University of Leeds, United Kingdom.
²⁷ Environmental Engineering, Yale University, USA.
²⁸ Institute of Environmental Assessment and Water Research, Department of Geosciences, Spanish National Research Council, Barcelona, Spain.
²⁹ Department of Building, National University of Singapore, Singapore.
³⁰ Aalto University, Finland.
³¹ Architectural Institute of Japan, Japan.
³² McGill University, Canada.
³³ Ergonomics and Aerosol Technology, Lund University, Sweden.
³⁴ College of Environmental Sciences and Engineering, Peking University, Beijing, China.

PMID: 32521345
PMCID: PMC7250761
DOI: 10.1016/j.envint.2020.105832

How can airborne transmission of COVID-19 indoors be minimised?

Lidia Morawska et al. Environ Int. 2020 Sep.

. 2020 Sep:142:105832.

doi: 10.1016/j.envint.2020.105832. Epub 2020 May 27.

Authors

Affiliations

¹ International Laboratory for Air Quality and Heath (ILAQH), WHO Collaborating Centre for Air Quality and Health, School of Earth and Atmospheric Sciences, Queensland University of Technology, Brisbane, Queensland, Australia. Electronic address: l.morawska@qut.edu.au.
² Respiratory Sciences, University of Leicester, Leicester, United Kingdom.
³ Department of Architectural Engineering, The Pennsylvania State University, USA.
⁴ Faculty of Architecture and the Built Environment, Delft University of Technology, the Netherlands.
⁵ REHVA (Federation of European Heating, Ventilation and Air Conditioning Associations), BBA Binnenmilieu, the Netherlands.
⁶ Department if Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, Italy.
⁷ Key Lab of Aerosol Chemistry and Physics Chinese Academy of Sciences, Xi'an, Beijing, China.
⁸ Edinburgh Napier University and NHS Lanarkshire, Scotland, United Kingdom.
⁹ Department of Medicine, University of Cambridge, United Kingdom.
¹⁰ Franchimon ICM, the Netherlands.
¹¹ Cambridge Centre for Lung Infection, Royal Papworth Hospital and Department of Medicine, University of Cambridge, Cambridge, United Kingdom.
¹² International Standards at ISSO, ISSO International Project, the Netherlands.
¹³ Ergonomics and Aerosol Technology Lund University, Lund, Sweden.
¹⁴ Department of Chemistry, and Cooperative Institute for Research in Environmental Sciences (CIRES) University of Colorado, Boulder, USA.
¹⁵ REHVA Technology and Research Committee, Tallinn University of Technology, Estonia.
¹⁶ Department of Mechancal Engineering, Hong Kong University, University of Hong Kong, Pokfulam, Hong Kong, China.
¹⁷ Department of the Built Environment, Eindhoven University of Technology (TU/e), the Netherlands.
¹⁸ Centre for Air quality Research and evaluation (CAR), University of New South Wales (UNSW), Sydney, New South Wales, Australia.
¹⁹ Civil and Environmental Engineering, VA Tech, USA.
²⁰ AiCARR, Politecnico di Milano, Italy.
²¹ International Centre for Indoor Environment and Energy, Department of Civil Engineering, Technical University of Denmark, Denmark.
²² Mechanical Engineering, University of Colorado, Boulder, USA.
²³ Environmental Health, School of Public Health, University of Maryland, USA.
²⁴ Department of Civil and Environmental Engineering, University of California, Berkeley, CA, USA.
²⁵ Faculty of Engineering and Science, Department of Civil Engineering, Aalborg University, Denmark.
²⁶ School of Civil Engineering, University of Leeds, United Kingdom.
²⁷ Environmental Engineering, Yale University, USA.
²⁸ Institute of Environmental Assessment and Water Research, Department of Geosciences, Spanish National Research Council, Barcelona, Spain.
²⁹ Department of Building, National University of Singapore, Singapore.
³⁰ Aalto University, Finland.
³¹ Architectural Institute of Japan, Japan.
³² McGill University, Canada.
³³ Ergonomics and Aerosol Technology, Lund University, Sweden.
³⁴ College of Environmental Sciences and Engineering, Peking University, Beijing, China.

PMID: 32521345
PMCID: PMC7250761
DOI: 10.1016/j.envint.2020.105832

Abstract

During the rapid rise in COVID-19 illnesses and deaths globally, and notwithstanding recommended precautions, questions are voiced about routes of transmission for this pandemic disease. Inhaling small airborne droplets is probable as a third route of infection, in addition to more widely recognized transmission via larger respiratory droplets and direct contact with infected people or contaminated surfaces. While uncertainties remain regarding the relative contributions of the different transmission pathways, we argue that existing evidence is sufficiently strong to warrant engineering controls targeting airborne transmission as part of an overall strategy to limit infection risk indoors. Appropriate building engineering controls include sufficient and effective ventilation, possibly enhanced by particle filtration and air disinfection, avoiding air recirculation and avoiding overcrowding. Often, such measures can be easily implemented and without much cost, but if only they are recognised as significant in contributing to infection control goals. We believe that the use of engineering controls in public buildings, including hospitals, shops, offices, schools, kindergartens, libraries, restaurants, cruise ships, elevators, conference rooms or public transport, in parallel with effective application of other controls (including isolation and quarantine, social distancing and hand hygiene), would be an additional important measure globally to reduce the likelihood of transmission and thereby protect healthcare workers, patients and the general public.

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Conflict of interest statement

Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

**Fig. 1**
Traditional infection control pyramid adapted from the US Centers for Disease Control (CDC, 2015).

**Fig. 2**
Engineering level controls to reduce the environmental risks for airborne transmission.

See this image and copyright information in PMC

References

1. Ai Z., Hashimoto K., Melikov A.K. Airborne transmission between room occupants during short-term events: Measurement and evaluation. Indoor Air. 2019;29:563–576. - PubMed
1. AIVC . Air Infiltration and Ventilation Centre; Brussels: 1996. A Guide to Energy Efficient Ventilation.
1. ASHRAE, 2017. ASHRAE Standard 52.2‐2017 Method of testing general ventilation air‐cleaning devices for removal efficiency by particle size.
1. ASHRAE, 2020a. COVID-19 (CORONAVIRUS) PREPAREDNESS RESOURCES. American Society of Heating, Ventilating, and Air-Conditioning Engineers.
1. ASHRAE, 2020b. Position Document on Airborne Infectious Diseases, Approved by the Board of Directors, January 19, 2014. Reaffirmed y the Technology Council, February 5, 2020. Atlanta, Georgia.

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How can airborne transmission of COVID-19 indoors be minimised?

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How can airborne transmission of COVID-19 indoors be minimised?

Authors

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Conflict of interest statement

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