A breath of fresh air: Addressing the impact of ventilation systems on the spread of COVID-19

Dr. Lexuan Zhong

We know that SARS-CoV-2, the virus that causes COVID-19 disease, is typically spread from person to person through “droplet transmission.” The droplets get expelled by an infected person when they cough, sneeze, or even speak—hence the need for physical distancing measures (to avoid close contact), frequent handwashing, and public health guidance on cleaning and disinfecting common surfaces.

But Dr. Lexuan Zhong, an Assistant Professor in the Department of Mechanical Engineering at the University of Alberta, believes that there is an important element missing from discussions about our collective efforts to curb the virus’s spread: airborne transmission.

Airborne transmission involves smaller particles that could, in theory, hitch a ride through heating, ventilation, and air conditioning (HVAC) systems. We don’t yet know how far SARS-CoV-2 could travel that way or how infectious those small particles might be, but that’s exactly what Dr. Zhong and her team intend to find out.

“Technically, we are conducting research to better understand the complex relationships between ventilation, pressure, air movement, moisture, droplet nuclei, filters, air purifiers, and mechanisms of airborne SARS-CoV-2 transmission (AST),” she explains. “But put simply, we’re studying how the virus moves through ventilation systems and how these systems can be designed or adapted to control the virus. Basically, we want to know if ventilation systems prevent AST or if they actually increase its spread.”

While it is frightening to think that HVAC systems could perpetuate AST in condo buildings, office towers, shopping malls, and schools, Dr. Zhong notes that the risk is still generally low. But given a recent account of how the direction and strength of air conditioning contributed to the spread of the virus at a restaurant in China, there is an urgent need for projects like this one to provide much-needed evidence that can then be used to bring that “low risk” as close to “no risk” as possible.

This type of research requires a blend of expertise from medical sciences and engineering, so Dr. Zhong has put together a multidisciplinary team. “Containing the COVID-19 outbreak is an extremely complicated issue that requires global efforts from different perspectives,” she says, and is quick to add that the project will capitalize on the team members’ strengths. Specifically, their work will involve: 1) conducting a systematic review of research on air circulation and viruses (i.e., gathering the body of evidence that already exists); 2) developing an effective strategy to reduce or halt the risk of AST through HVAC systems; and 3) testing that strategy on buildings at the University of Alberta’s campus in Edmonton. The ultimate goal of the project is to develop guidelines to support the safe use of HVAC systems, whether it be through new designs, modifications to existing models, or changes to maintenance operations.

“This work has the potential to impact millions of people living and working in high-occupancy structures,” says Dr. Zhong. “The spread of airborne infections in these types of enclosed spaces can have rapid, extensive, and detrimental consequences. Non-pharmaceutical interventions, such as those related to mechanical ventilation systems in buildings, could be a critical way to contain the current pandemic—or to mitigate outbreaks in the future.”

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