Seven important lessons regarding the vital role of ventilation in curbing the spread of airborne pathogens during the COVID-19 pandemic have been detailed in a recent article.
The article, found in the journal Science, comprises insights from renowned air quality experts: Professor Lidia Morawska, Professor Yuguo Li from The University of Hong Kong, and Professor Tunga Salthammer from the University of Surrey, UK.
Professor Morawska, who leads THRIVE at QUT’s School of Earth and Atmospheric Sciences, expressed that the swift global dissemination of COVID-19 quickly revealed the world’s lack of preparedness to tackle such a crisis.
“Initially, the World Health Organization and numerous national health bodies asserted that the virus was ‘not airborne’ but predominantly found on surfaces. This created a false impression regarding the virus’s transmission pathways,” noted Professor Morawska.
“Public health authorities dismissed established knowledge, resulting in misguided control strategies that focused on sanitizing surfaces rather than prioritizing ventilation, air filtration, face masks, and the deactivation of airborne viruses.”
“Nevertheless, experts in science and building engineering recognized from the outset that the virus was primarily transmitted through the air. The most effective way to minimize infection risks was to eliminate the virus from indoor air via ventilation or to neutralize it with UVC light.”
The co-authors of the paper outlined seven key lessons important for improving indoor air quality (IAQ):
1. The first lesson emphasizes the need for interdisciplinary collaboration in public health decision-making.
In the early pandemic phase, advisers to the WHO were predominantly public health specialists, which led to underappreciation of the contributions from physical, chemical, and engineering disciplines.
For instance, many current epidemiological studies investigating outbreaks often overlook ventilation rate measurements, leading to an incomplete understanding.
2. Beyond just opening windows for ventilation: relying solely on natural ventilation in buildings not constructed for efficient airflow is insufficient.
Mechanical ventilation systems must be incorporated into the solution as they provide various techniques for air distribution, including mixing, displacement, and personal ventilation, as well as disinfection through germicidal ultraviolet light and filtration.
3. The intersection of building design and ventilation: Modern buildings—whether homes, offices, shopping centers, airports, train stations, or schools—are increasingly complex yet often designed without sufficient focus on ventilation.
Proper ventilation, essential for making buildings habitable, frequently ranks low among primary design considerations. Therefore, building and ventilation design should be prioritized together in planning and execution.
4. Equivalent ventilation solutions for existing structures: Facilities such as care homes and schools that rely on natural ventilation often cannot be easily upgraded. Hence, alternative ‘equivalent ventilation’ methods are needed, utilizing air filtration and germicidal ultraviolet radiation.
While filtration does not eliminate water vapor, carbon dioxide, or gas pollutants, it effectively serves as an ‘equivalent to ventilation’ concerning particulate matter. Furthermore, germicidal UV light can deactivate airborne pathogens, thus contributing to infection control as well.
5. Developing ventilation control and risk assessment tools: Although risk assessment tools can help evaluate the danger of airborne infections, they are currently too complicated for daily management in modern buildings. There are ongoing efforts to research and develop new technologies specifically aimed at improving building ventilation systems.
6. Ongoing performance monitoring of ventilation systems: It’s vital to continuously monitor ventilation performance while buildings are occupied to adjust ventilation controls based on use and occupancy.
Many modern buildings are outfitted with CO2 monitors, and numerous cost-effective CO2 sensors are available for consistent monitoring in homes and transport systems, where non-dispersive infrared (NDIR) is the preferred method for measuring CO2.
Today’s devices are calibrated against established methods, with performance enhancements possible through machine learning techniques. Combining these with other relevant metrics is encouraged.
7. Mandating IAQ in public buildings: Indoor air quality must be regulated and managed in the same rigorous manner as food and water, necessitating action from relevant authorities. Our experiences during the pandemic confirmed that without regulations, achieving good IAQ cannot rely solely on the efforts of occupants or even building operators, particularly if the building was not originally designed with adequate systems.
The COVID-19 pandemic illustrated that ventilation is not only a crucial measure for reducing airborne infection risks but must also be integrated into strategies for improving IAQ against outdoor pollution.
“Ventilation and indoor airborne infection transmission: Lessons learned from the COVID-19 pandemic” is featured in Science.
