Clearing the air — literally — on Ontario schools

Good ventilation reduces the risk of COVID-19 transmission. So what’s being done to improve the air kids breathe?

Prior to the pandemic, public health in Niagara didn’t play much of a role in ventilation, says acting medical officer of health Mustafa Hirji. “It wasn’t part of our mandate or something we had much expertise in.” But that changed as the pandemic progressed, and “we realized that this virus actually spreads through the air, and ventilation can be one of the tools that stops its spread,” Hirji says.

Leading health organizations agree that good ventilation reduces the risk of COVID-19 transmission. “People are becoming more conscious about the importance of ventilation and its effects,” says Toronto engineer Joey Fox, who specializes in heating, ventilation, and air-conditioning automation in schools. HVAC systems have come under more scrutiny since the Ontario government made masking optional in schools on March 21. “This is a societal issue” that affects more than just schools, Fox says. “The issue of schools is you have so many kids in one place, and they’re forced to be there.”

Hirji, who has, since the province lifted most restrictions, encouraged the voluntary use of pandemic measures such as masking and proof of vaccination, says few government-led COVID-19 protections remain for children. “[Ventilation is] actually the one protection that [keeps] me from saying that all of them are gone, as opposed to most of them are gone.”

Few govt-led #COVID19 protections remain for children; let's exercise the ones we control to avoid seeing more children in hospitals:
- Get kids vaccinated
- Keep them wearing masks
- The rest of us do the same—don't spread COVID-19 to them!

So what’s the environment like in Ontario schools — and how can parents and guardians, teachers, and students get informed about the air they breathe?

How does school ventilation work?

The “backbone of HVAC” is a heating plant (or boiler plant) that heats up water and passes it around a school, Fox says. Newer schools may also have chiller plants (or cooling plants) that cool the buildings down. There are also air-handling units, which provide ventilation by bringing in outdoor air.  

Fox says that older buildings tend to have old and less efficient equipment; many of them also use natural ventilation, meaning they “rely on leakage through windows to provide most of the outdoor air, instead of actually bringing outdoor air into the classrooms.” This is inferior to mechanical ventilation (using HVAC systems) and can lead to discomfort and poor health, he says. It’s not easy to fix ventilation in an old building, Fox says. “A building is built in a certain way. But this needs to be a societal obligation moving forward. It requires significant investment.”

Ontario’s Ministry of Education tells via email that fewer than 10 per cent of publicly funded schools are without mechanical ventilation and notes that all learning spaces that lack it have a high-efficiency particulate air-filter unit, which help filter bacteria and viruses in the air. The government says it had delivered more than 73,000 HEPA units to schools by the start of the school year and is deploying 49,000 more to schools and child-care spaces.

Niagara's acting medical officer of health says we've learned about the importance of ventilation thanks to the pandemic. (Niagara Region Public Health/YouTube)

What’s been done to improve ventilation in schools?

“In Ontario, the Ministry of Education, more than anyone else, actually invested a lot of money to improve school ventilation,” Fox says. “There's been a lot of good work done. Of course, there's always room to improve, but this has been the best example in Canada.” He does suggest adopting “a bigger focus on improving the filtration quickly in places that are under-ventilated and making sure that the HEPA filters are properly sized.”

The Ministry of Education tells via email that all its school ventilation systems have been assessed and that 99 per cent of schools are using MERV-13 filters (high-grade filters capable of trapping viral particles) and/or changing filters more frequently. It also says 99 per cent of schools are running ventilation systems longer and increasing fresh-air intake. The ministry notes that “some measures may not be feasible within the context of a school facility/site and related building systems.”

School-level information outlining ventilation improvements and the number of HEPA units is publicly available across boards, the ministry official adds. For example, the DSBN has an online tool with which one can see the ventilation improvements in place at each school.

In an email statement to, a spokesperson for the District School Board of Niagara (that region’s public board) says 90 per cent of its schools have mechanical ventilation. By September 2021, “we replaced all filters in ventilation systems, replaced exhaust fans, adjusted equipment controls and re-commissioned air handling systems in all our facilities.” Last year, nine schools received “major HVAC retrofits”; 10 additional schools will be retrofitted this year. The board notes it has added HEPA filters to areas in which they’re not required by the province, “such as music rooms and childcare centres.”

How is school ventilation monitored?

Fox says the responsibility for managing school ventilation varies by board. Often, he says, a building caretaker oversees systems, while inspections are handled by contractors or a dedicated facilities-management team. But, he adds, the people in charge of routine operation are not always properly trained. The DSBN spokeperson tells that “this kind of work is performed by trained specialists” in its schools, not caretakers.

Building Monitoring & Operations - This is where the biggest problem with ventilation occurs. It's designed one way and works for a couple of years. There is no oversight for HVAC mechanics/maintenance technicians. People operating buildings take their word.

“The burdens of trying to make sure people are fully trained on how to diagnose problems and get them resolved — that’s a big undertaking,” Fox says, emphasizing that education and awareness matter. He says he recently went to the dentist and found the HVAC system in the office was off. “A broken fan or a fan that’s off is a big problem. It’s a health problem and people just don't know. They’re not aware.”

According to the ministry, school boards are responsible for implementing ventilation and filtration best practices, including using properly sized HEPA units, ensuring systems are assessed and in good working order, and opening windows “when safe to do so and appropriate.”  

DSBN’s official ventilation strategy involves regularly inspecting systems and replacing filters, as well as monitoring the concentration of carbon dioxide in school spaces.

Since people breathe out CO2 when they exhale, measuring the concentration of the gas in a space is a way to indicate how good the ventilation is. “If you want to know what the air quality is, wherever you are, the best way to do it is just to measure the CO2 levels,” Fox says.

According to Hirji, Niagara public-health inspectors carry carbon-monoxide monitors that also measure CO2. They’ve used these in congregate-living settings for several months, and Hirji hopes to bring monitoring to other spaces public-health regularly inspects, such as restaurants, tattoo parlours, and indoor pools.

Earlier in the pandemic, he says, inspectors would monitor ventilation in schools that had COVID-19 cases, but “with the huge increase in infections we’re now seeing — at least 50 per cent of Niagara schools have an infection that we are aware of, and that’s just from parents voluntarily informing us that their child tested positive — we’re no longer able to do that kind of follow-up.”

Since January, Niagara public health has recommended that schools conduct their own CO2 monitoring periodically to confirm good-quality ventilation and raise any issues with public health. “We don’t have an exact schedule for CO2 monitoring, but I can confirm that it is done regularly and thoroughly in our schools,” the DSBN spokesperson writes.

 How to check ventilation yourself

Fox has shared tips on Twitter for people who want to independently check the ventilation in the spaces they’re in. For example, he recommends taping a small piece of plastic to a diffuser to see whether it moves, because that provides a visual sense of how much air is coming into a room. “We need to improve the systems,” he says. “And, unfortunately, one of the best ways — I wish it didn’t have to be this way — is to educate the occupants and to get them to speak up for themselves.”

Fox applauds a new program in Peterborough that sees the public-health unit teaming up with the library to lend out monitors, along with a package of instructions.

Jennifer Jones, the Peterborough Public Library’s CEO, says the kits, which normally cost about $300 but can be borrowed free for a week with a library card, are “super simple” to use and give people useful information they can act on: “Having it for the week gives you the time to make changes and adapt your environment a little bit to see if what you did caused a change to the readings.”

The DSBN says anyone concerned about ventilation in one of its schools or interested in doing independent CO2 monitoring should contact the principal to investigate it. But, they add, “we do have designated experts, including indoor air quality specialists, to perform this type of work.”

While school boards can use monitors, “reading interpretation and mitigation decisions should be made with consideration of issues identified in Public Health Ontario’s guidance,” the Ministry of Education says.

What happens next?

Hirji and Fox agree public health and engineers should collaborate more on ventilation. Hirji says that ventilation is not a panacea and that he’s concerned it’s all the province is relying on now. That said, he does think studying COVID-19 and ventilation has been a game-changer. “I believe that probably influenza, common colds, and most other respiratory viruses are actually transmitting through the air. [This] has called into question our previous paradigm that these infections were largely spread through droplets.”

By promoting ventilation in public settings, he says, “we’re hopefully not just combatting COVID-19 … but we’re hoping we can mitigate flu seasons as well.”

One way to work toward this would be prioritizing ventilation in new buildings, Hirji suggests, perhaps by improving standards in building codes. “That’s one way to make sure we take this new knowledge of information and filtration, and we actually apply it broadly throughout our society.”

For Fox, this is an important effort — and one that must be led from the top. “When you’re creating a safe environment, there are no demands on [individuals],” Fox says. “It’s a societal responsibility of ensuring that the our spaces have clean air, and that’s one of the best ways forward. That’s how we live with COVID.”

This article is written by Justin Chandler

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