“Paradigm Shift” to Fight Airborne Spread of COVID-19 Indoors

Then in the early 20th century, American public health expert Charles Chapin erroneously attributed respiratory infections caught in close proximity to other people to large droplets produced by an infected person, which fall quickly to the ground. As a result, he stated that airborne transmission was almost impossible. 

Yet in 1945, scientist William Wells published a paper in the predecessor to Science, lamenting that while we were investing in disinfecting water and keeping our food clean, we had done nothing for our indoor air, given the denial of airborne transmission. His research on measles and tuberculosis—caused by airborne pathogens—challenged this notion in the 20th century, but didn’t break it. 

Now that the research on SARS-CoV-2 finally has brought to light that many respiratory diseases can be transmitted through the air, researchers argue that we must take action.

“Let’s now not waste time until the next pandemic,” said co-author Jose-Luis Jimenez, fellow in the Cooperative Institute of Research Sciences (CIRES) and professor of chemistry at CU Boulder. “We need a societal effort. When we design a building, we shouldn’t just put in the minimum amount of ventilation that’s possible, but instead we should keep ongoing respiratory diseases, such as the flu, and future pandemics in mind.”

The long-standing misunderstanding of the importance of airborne transmission of pathogens has left a large gap of information in how to best construct and manage building ventilation systems to mitigate the spread of disease—with the exception of some manufacturing, research and medical facilities. Instead, buildings have focused on temperature, odor control, energy use and perceived air quality. So while there are safety guidelines for chemicals such as carbon monoxide, there are currently no guidelines, globally or in the U.S., that regulate or provide standards for mitigating bacteria or viruses in indoor air resulting from human activities.

“Air in buildings is shared air—it’s not a private good, it’s a public good. And we need to start treating it like that,” said Miller.

Lidia Morawska, lead author on the article and director of Queensland University of Technology’s International Laboratory for Air Quality and Health, said there needs to be a shift away from the perception that we cannot afford the cost of control. She notes that the global monthly cost from COVID-19 had been conservatively estimated as $1 trillion and the cost of influenza in the U.S. alone exceeded $11.2 billion annually.

While detailed economic analysis has yet to be done, estimates suggest necessary investments in building systems may be less than 1% of the construction cost of a typical building.

Ventilation systems should also be demand-controlled to adjust for different room occupancies, and differing activities and breathing rates, such as exercising in a gym versus sitting in a movie theatre, according to Morawska. For spaces that cannot improve ventilation to an appropriate level for the use of the space, she said air filtration and disinfection will be needed.

Because buildings consume over one-third of energy globally, much from heating or cooling outdoor air as it is brought indoors, it would be useful to design a “pandemic mode,” that would allow for buildings to only use more energy when necessary, said Jimenez.

The researchers also call for national comprehensive indoor air quality (IAQ) standards to be developed and enforced by all countries, and for this information to be available to the public. 

For this to happen, however, many more than scientists will need to understand its importance.

“I think there is a certain amount of demand that needs to start coming from the consumer and from the person who works in these indoor spaces in order to push change,” said Miller.