Importance of ventilation and/or air cleaning in relation to risk of indoor transmission of infectious diseases: Insights from Prof. Lidia Morawska
05 February 2025
In a recent interview in February 2025, Professor Lidia Morawska shared her knowledge and experiences about indoor air quality and disease transmission, offering a view of current understanding and future directions in the field. The interview discussions are summarized below:
Key Transmission Factors
Professor Morawska outlined three essential elements for respiratory disease transmission: an infected person present in the space, susceptible individuals sharing that space, and conditions allowing pathogen accumulation. She emphasized that both the concentration of pathogens and exposure time are key factors in transmission risk.
Professor Morawska outlined three essential elements for respiratory disease transmission: an infected person present in the space, susceptible individuals sharing that space, and conditions allowing pathogen accumulation. She emphasized that both the concentration of pathogens and exposure time are key factors in transmission risk.
Shifting Understanding of Transmission Routes
Professor Morawska highlighted how public health authorities’ understanding of COVID-19 transmission evolved globally from an initial focus on surface contamination to recognition of airborne transmission as the primary route, drawing on scientific knowledge from recent decades. Professor Morawska clarified the misconception about infectious respiratory particle sizes, explaining that the traditional medical distinction between aerosols (below 5 micrometres) and droplets (above 5 micrometres ) has been abolished, as all respiratory particles larger than about 100 micrometres can be airborne and contribute to infection transmission.
Professor Morawska highlighted how public health authorities’ understanding of COVID-19 transmission evolved globally from an initial focus on surface contamination to recognition of airborne transmission as the primary route, drawing on scientific knowledge from recent decades. Professor Morawska clarified the misconception about infectious respiratory particle sizes, explaining that the traditional medical distinction between aerosols (below 5 micrometres) and droplets (above 5 micrometres ) has been abolished, as all respiratory particles larger than about 100 micrometres can be airborne and contribute to infection transmission.
Environmental Factors
The professor detailed how environmental conditions affect respiratory droplets. When expelled, water-based particles quickly shrink to 20-40% of their original size due to evaporation. Interestingly, recent research has shown that CO2 levels as low as 700-800 ppm can increase SARS-CoV-2 virus stability through increased acidity of respiratory particles containing the virus.
The professor detailed how environmental conditions affect respiratory droplets. When expelled, water-based particles quickly shrink to 20-40% of their original size due to evaporation. Interestingly, recent research has shown that CO2 levels as low as 700-800 ppm can increase SARS-CoV-2 virus stability through increased acidity of respiratory particles containing the virus.
Ventilation vs. Air Cleaning
While air-cleaning technologies can be helpful, Professor Morawska stressed that proper ventilation should be the primary focus. She discussed challenges with air purifiers in schools, noting that issues like noise often result in their underuse. She advocated that there is much room to improve these purifiers in terms of equipping them with lower pressure and lower noise filters and designing them to operate autonomously in response to pollutant concentrations above set limits
While air-cleaning technologies can be helpful, Professor Morawska stressed that proper ventilation should be the primary focus. She discussed challenges with air purifiers in schools, noting that issues like noise often result in their underuse. She advocated that there is much room to improve these purifiers in terms of equipping them with lower pressure and lower noise filters and designing them to operate autonomously in response to pollutant concentrations above set limits
Future Preparedness
Rather than focusing solely on future pandemics, Professor Morawska stressed the need to tackle existing respiratory diseases and epidemics they cause and do our best to reduce the risk of infection from the known pathogens we’re dealing with now. She recommended a layered approach combining proper ventilation, appropriate use of masks in high-risk situations, and awareness of indoor air quality.
Rather than focusing solely on future pandemics, Professor Morawska stressed the need to tackle existing respiratory diseases and epidemics they cause and do our best to reduce the risk of infection from the known pathogens we’re dealing with now. She recommended a layered approach combining proper ventilation, appropriate use of masks in high-risk situations, and awareness of indoor air quality.
Personal Protection Strategies
Professor Morawska carries a CO2 meter and masks (preferably N95) for personal protection. She emphasized that while individual responsibility is important, building operators should ultimately be responsible for maintaining good indoor air quality.
Professor Morawska carries a CO2 meter and masks (preferably N95) for personal protection. She emphasized that while individual responsibility is important, building operators should ultimately be responsible for maintaining good indoor air quality.
This interview highlights the complexity of indoor air quality management and the need for a comprehensive approach to reducing disease transmission in shared spaces. These perspectives provide guidance for the MIST project's ongoing efforts to develop solutions for healthier indoor environments and reduced disease transmission risks.
Professor Lidia Morawska will join us as a keynote speaker for the MIST event 2025 on June 2nd!
📅 Don’t miss this opportunity to explore the future of indoor air quality!
Professor Lidia Morawska will join us as a keynote speaker for the MIST event 2025 on June 2nd!
📅 Don’t miss this opportunity to explore the future of indoor air quality!
🔗 Learn more: https://www.aanmelder.nl/mistevent
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Time: 13:30 - 18:00
Location: Berlagezaal, Faculty of Architecture and Built Environment, Delft University of Technology
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05 February 2025
Importance of ventilation and/or air cleaning in relation to risk of indoor transmission of infectious diseases: Insights from Prof. Lidia Morawska
We are delighted to announce that Professor Lidia Morawska, a world-renowned expert in indoor air quality, will join us as a keynote speaker for the MIST event 2025 on June 2nd!
In a recent interview, Professor Lidia Morawska outlined evidence-based approaches for improving indoor environments through ventilation, effective air-cleaning technologies, and comprehensive monitoring systems.
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