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The race to make indoor air safer ahead of another COVID-19 winter

Many campuses have spent recent months conducting emergency retrofits of HVAC systems, installing new hardware and devising novel solutions for older buildings.


In July 2020, 239 scientists from around the world penned an open letter to the World Health Organization (WHO) that landed like an epidemiological bombshell. SARS-CoV-2, it said, was airborne, spreading not just through large droplets but through aerosolized particles that could linger in the air longer and drift farther distances.

“Infection-control epidemiology had really drunk from this well of large-droplet transmission,” said Colin Furness, an epidemiologist and assistant professor at the University of Toronto’s faculty of information. “But the data had just stopped making sense.” Outbreaks were spreading in indoor settings far more rapidly than seemed possible if the disease wasn’t airborne.

Besides proving to be a transformative moment for the study of this deadly new virus, it meant that ventilation and air purification began to displace surface sanitizing, and even two-metre distancing, at the top of the list of public-health interventions. Many institutions – from the WHO to some provincial governments – have been slow to adapt. But one kind of institution, said Dr. Furness, was quick out of the gate.

“Universities tend to be pretty smart,” he said. “If you go back a few thousand years, you’ll find universities are some of the most successful corporate structures around, because they adapt better than just about any other organization [….] It’s not surprising they’d look at this new information and say, ‘What do we do now?’”

Rob Glass, Brock’s manager of mechanical services, with one of the new air purifiers being installed in all Brock classrooms and teaching labs. Photo courtesy of Brock University.

Across the country, there is ample evidence of those changes. Campuses spent this past summer conducting emergency retrofits of heating, ventilation and air conditioning (HVAC) systems, installing new hardware and coming up with novel solutions for older buildings without central heating and cooling.

Most have looked to guidance from the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), which issues guidelines to building managers across North America. In April 2021, it released an “unequivocal statement” acknowledging airborne transmission and recommending major changes to building systems.

Some of the most important included improving HVAC system filtration to what is called MERV 13 which filters out a greater percentage of virus-sized particles. Or increasing the number of air changes per hour in occupied rooms and introducing HEPA filters, which remove particles as small as 0.3 microns, to scrub air in rooms not equipped with HVAC systems.

“We take a lot from ASHRAE,” said Dave McArthur, director of facilities and services at Brock University. “Early in the pandemic they recommended full fresh air all the time, which changed to what they call ‘equivalent air changes’ – basically freshening the air with filtration and purifiers.”

Brock now aims for six fresh-air equivalent changes per hour, and has begun flushing indoor air hours before a building or room is occupied as well as after it’s vacated, rather than simply shutting the system down. All of this represents a break from previous priorities around maximizing energy efficiency. “What we’re doing now is the least energy-efficient thing,” said Mr. McArthur. “Imagine bringing in 100 per cent fresh outdoor air when it’s 30 degrees and 90 per cent humidity outside.”

There are other challenges too: bringing in large amounts of humid outdoor increases the risk of mould and will ultimately require more maintenance, and in winter, cold outdoor air will need to be heated.

‘Going above and beyond’

Similar efforts are underway at many other postsecondary institutions. At Dalhousie University, for example, a facilities team assessed more than 600 indoor spaces this summer to see where air filtration and fresh-air intake had to be improved to meet upgraded safety standards. Meanwhile, the University of Alberta is aiming to reach three to six air changes per hour in indoor spaces, which is estimated to provide a 78 to 95 per cent reduction in SARS-COV-2 transmission.

At York University, director of property management Stewart Dankner is trying to help make the HVAC systems operate more like those of the medical facilities at Toronto’s University Health Network, where he used to work until July 2020. That has meant running HVAC fans 24 hours a day, updating filters to MERV 13, and installing HEPA filters in structures such as Glendon Hall, a building that dates to 1924 and has no central HVAC system.

Mr. Dankner is also keeping a close eye on regulating humidity. “We have a minimum humidity level that we keep in operating rooms, of between 30 and 50 per cent,” he said. “When the air is humid, the virus particulate doesn’t have that opportunity to free float in the air as much.”

The U of T’s campus ventilation efforts are similar to those at York. Dr. Furness said the goal is to reach MERV 13 campus-wide (up from MERV 8), add more air changes, and install HEPA filters in buildings that have no HVAC systems. “It looks proactive to me, it looks like it’s going above and beyond,” he said. Dr. Furness is teaching one class in person this term, and brings a portable carbon dioxide monitor to class with him to gage how fresh the air is. “The readings are very low, resembling outdoor air much of the time,” he said. “My own experience is that I can’t imagine feeling safer than right now.”

Precautionary principle

However, there are still questions about the strategy being followed on some campuses. Michael Arfken, an associate professor of psychology and president of the faculty association at the University of Prince Edward Island, says he has been trying since summer to get a clearer understanding of the university’s ventilation-improvement strategy, without much success.

UPEI has commissioned a consultant report on air quality and ventilation, but has yet to release it. The university has also said it’s following provincial occupational health and safety guidelines, but these haven’t been updated to reflect best practices when it comes to COVID-19.

“There is in law what’s known as the precautionary principle,” said Dr. Arfken. “When you’re not totally sure what’s reasonable, you need to take precautions above and beyond what may be in the legislation. And in fact, air-quality experts are saying that the standards that exist today are not sufficient for dealing with this new sort of situation. Do employers have to wait for the provincial legislation to be updated in order to address a dynamic situation?”

While the pandemic will eventually end, questions around how to mitigate the risk of viral illnesses generally, will likely be with us much longer. At York, Mr. Dankner believes there will likely be permanent changes to the way his profession operates. He foresees the potential for more high-tech solutions, like HVAC systems outfitted with germicidal ultraviolet lights. He also expects a general culture change within the profession.

“I think what you’re going to see is more proactive efforts,” he said. “We’ll see electronics or smart buildings able to predict ventilation problems earlier, or portable HEPA filtration with built-in alarms to tell us when the systems are dirty. I think that will be a change for the future, moving more toward prevention, rather than reaction.”

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