The COVID-19 pandemic has highlighted the essential role of indoor air quality in preventing the spread of airborne pathogens. 

Air quality experts have outlined crucial lessons learned about ventilation in a study published in Science.

At the start of the COVID-19 pandemic, global health authorities, including the World Health Organisation (WHO), believed that the virus spread mainly through contaminated surfaces. 

However, it soon became evident that airborne transmission was the dominant mode of spread. 

Professor Lidia Morawska, who leads the International Laboratory for Air Quality and Health at QUT, points out the significance of this shift.

“In the early days of the pandemic, the World Health Organisation and many national health authorities claimed the virus was ‘not in the air’ but rather present in large quantities on surfaces. This led to a misconception about how the virus was transmitted,” she said. 

This early misunderstanding resulted in a focus on surface cleaning rather than more effective measures such as ventilation and air filtration. 

Despite this, the scientific community quickly recognised that ventilation was crucial to reducing the risk of airborne infections. 

“For science and building engineering experts, there was no doubt from the beginning that the virus was transmitted predominantly through the air,” Professor Morawska noted. 

The study identifies several critical areas for improvement. 

Public health decision-making must incorporate insights from physical, chemical, and engineering sciences, which have often been undervalued in epidemiological studies that neglect to consider ventilation rates. 

Additionally, the reliance on natural ventilation, such as simply opening windows, is insufficient in modern buildings. 

Mechanical ventilation systems, including air disinfection through ultraviolet germicidal irradiation (UVGI) and filtration, are necessary to ensure adequate air quality.

Additionally, researchers say building design must prioritise effective ventilation. 

Different types of buildings, including offices, schools, and transport hubs, require tailored ventilation strategies to meet their specific needs. In older buildings where retrofitting with modern ventilation systems is impractical or costly, alternative solutions like air filtration and UVGI can offer comparable levels of infection control.

The development of new technologies is considered essential for simplifying ventilation control and risk assessment, making these tools more accessible for everyday use in contemporary buildings. 

Continuous monitoring of ventilation performance, particularly when buildings are occupied, is also crucial. This can be achieved through the use of CO2 sensors and other devices that provide real-time data to optimise air quality based on changing occupancy levels.

The scientists call for indoor air quality to be regulated with the same rigour as water and food safety. 

They say that without formal regulations, ensuring consistently good air quality cannot be left to building operators or occupants alone.