Plexiglass could be ‘counterproductive’ for good COVID-19 ventilation, experts say

Some health experts are urging institutions and institutions to rethink the use of plexiglass as a measure against COVID-19, arguing that the barriers could even be “counterproductive” when they impede the ventilation needed to prevent the spread of the more communicable to avoid delta variant.

Since the start of the pandemic, plastic barriers have become a common sight in shops and schools.

But just as the coronavirus has evolved since then, experts say our understanding of the efficacy of those barriers must evolve too — especially as colder weather and relaxed pandemic rules mean more people are indoors.

dr. Peter Juni, an epidemiologist at St. Michael’s Hospital in Toronto and a member of the Ontario COVID-19 Science Advisory Table, wants people to “throw the plexiglass away” in most situations.

“The challenge with Plexiglas walls, if not implemented very selectively, is that they can impede ventilation even if the air cannot circulate properly,” Juni told CBC News.

Peter Juni
dr. Peter Juni, an epidemiologist at St. Michael’s Hospital in Toronto and a member of the Ontario COVID-19 Science Advisory Table, wants people to “throw the plexiglass away” in most situations. (Zoom)

“If you start to fragment the room unnecessarily with plexiglass walls, it’s actually counterproductive because the air can’t circulate properly,” he said.

“And there’s even some observational evidence to suggest that this could make things worse rather than better.”

dr. Raj Bhardwaj, a physician and clinical associate professor at the University of Calgary, previously told to CBC Radios Information morning Moncton that the delta variant “has evolved to be more efficient through air transfer”, making ventilation essential when it comes to reducing risk.

VIEW | Experts reconsider using Plexiglas to prevent the spread of COVID-19:

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Rethinking the use of plexiglass to prevent the spread of COVID-19

Experts say Plexiglass barriers may not be the most effective way to prevent the spread of COVID-19 and may hinder ventilation in certain environments. 2:01

“Those plastic barriers … can interfere with the normal ventilation of a room, they can create dead zones where the air stagnates, and those viral particles in the air can build up over time,” he said.

“They can help prevent a direct hit from someone who talks damply to you or sneezes at you when they’re not wearing a mask… move the aerosol cans to another part of the room.”

‘Important in certain situations’

dr. However, Bonnie Henry, BC’s provincial health officer, says barriers make a difference to those who interact closely with the public in high volumes.

“Barriers are important in certain situations, and I think of fast food restaurants and coffee shops if that barrier does protect you from the person on the other side of them,” she said at a news conference Tuesday.

“On their own, they’re not everything, but they definitely make the difference.”

Jeff Siegel, a professor of civil and mineral engineering at the University of Toronto who studies indoor air quality, welcomed Juni’s recommendation to remove Plexiglas because of concerns about airflow, but also agrees with Henry that they can be helpful in certain workplaces.

Jeff Siegel
Jeff Siegel, a professor of civil and mineral engineering at the University of Toronto who studies indoor air quality, says barrier restricts airflow but can sometimes facilitate distance. (CBC)

“There are times when you want to keep people apart, and sometimes a physical barrier is the easiest way to do that,” he told CBC News, noting that barriers make more sense in a tighter space like a grocery store checkout. than in an office environment.

“If you’re going to do a barrier, do it right,” Siegel said.

“[It] should be big enough… to really prevent a lot of the drops from getting through.”

Multi-layered approach

Experts say the best defense against COVID-19 indoors is a multi-layered approach that includes good ventilation.

“What you want is really just good ventilation, reasonable cleaning … enough stuff to disinfect your hands and good masks,” Juni said.

“That is certainly much more important [than plexiglass].”

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Students will be seen through individual Plexiglas shields at a Montreal school in August 2020. (Paul Chiasson/The Canadian Press)

Companies that have invested thousands of dollars in barriers may feel frustrated by calls to dump them, which Siegel says is “a very reasonable response” due to past COVID-19 reports.

“I understand why people are angry, but the reality is that the evidence is changing,” he said.

“While we had very good reasons to think that Plexiglas could have made a difference then, we now know that there are more challenges.”

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