As students return to campus for the fall semester, The Varsity considered U of T’s ventilation and filtration mechanisms with Colin Furness — an assistant professor at the Institute of Health Policy, Management, and Evaluation — and Jeff Siegel — a professor in the Department of Civil and Mineral Engineering. Both Siegel and Furness discussed the ability of effective filtration to reduce the risk of transmission of airborne pathogens and expanded on their concerns with the gaps in U of T’s current filtration systems. 

The University of Toronto Students’ Union had previously criticized the delays in information regarding the university’s ventilation and filtration procedures, and had also expressed concerns with the procedures themselves. Following that criticism, the university administration assured the U of T community of the strength and effectiveness of its ventilation and filtration plan

Ventilation and filtration basics

Furness highlighted the vital role that air quality plays in efforts to combat the ongoing pandemic. “We need vaccination, we need people to behave responsibly, [and] we need a functioning health-care system,” he said. “But really, in terms of being able to get back to normal, we need to manage our air like we’ve managed our water — that is to say, we make sure it’s clean before we drink it.” 

Two procedures underlie ensuring that air is clean: ventilation, which involves replacing inside air with fresh air from outside, and filtration, which involves cleaning recirculated air. 

The importance of ventilation and filtration stems from the airborne nature of SARS-CoV-2 — the specific type of coronavirus responsible for the COVID-19 pandemic. “[SARS-CoV-2] is airborne, and that’s something that provincial governments haven’t actually acknowledged,” said Furness. 

Although the World Health Organization recognized airborne transmission of COVID-19 in December 2021, the province of Ontario hasn’t mandated any additional measures to increase air quality. 

Furness believes that this situation represents a missed opportunity. “If you have maximum ventilation… the air is a lot like outdoor air. What we know from studying viruses generally and COVID in particular [is that the] outdoors is a lot safer than indoors,” continued Furness.

Siegel pointed out that adequate ventilation and filtration pose benefits beyond just reducing COVID-19 transmission. “We have a variety of other respiratory diseases that are common every year,” he said. Such illnesses not only pose a danger to peoples’ health, particularly for more vulnerable populations, but also interrupt learning. “I would argue that any of the investments we make in things like ventilation will pay off for those things as well,” said Siegel. 

A 2013 study by the United States National Library of Medicine found that Heating, Ventilating, and Air Conditioning (HVAC) filtration systems contributed to reduced risks of certain airborne pathogens, including rhinovirus, which is involved in common cold; influenza; and coronavirus. 

State of campus buildings

In April 2021, U of T’s Utility and Operations and Environmental Health and Safety jointly performed an assessment of the university’s HVAC systems. Following this assessment, they created a list of recommendations to guide the university’s ventilation and filtration policy, all of which the university implemented. 

The university’s HVAC procedures now include starting up ventilation systems two hours before a building opens and disabling controls on ventilation systems that reduce airflow. 

The university also affixed filters rated Minimum Efficiency Reporting Value-13 (MERV) — filters able to capture smaller particles that can pass through the air. According to Furness, “MERV 13 is considered adequate for infection control purposes, and the gold standard is MERV 16.” 

Out of the 107 buildings on the St. George campus not operated by the federated colleges, 23 do not contain central mechanical ventilation, including the University of Toronto Graduate Students’ Union, the Sir Daniel Wilson Residence, and Whitney Hall. However, many of the most frequented buildings on campus — including Hart House, Robarts library, and Sidney Smith Hall — contain HVAC systems with filters rated MERV 13 or higher. At the Mississauga and Scarborough campuses, all buildings are outfitted with filters rated MERV 13 or higher. 

The university is also committed to ensuring that each classroom receives six equivalent air changes per hour (ACH) when in use, the same standard applied to health care settings. Also, the university measures the ACH in every classroom in the university. 

For classrooms that do not meet the six ACH threshold, the university limited use of the room, altered existing HVAC equipment to allow the room to meet the threshold, or installed localized air filtration units to supplement the air flow rate. 


When asked about potential gaps in U of T’s HVAC strategy, Siegel cited the university’s broader COVID-19 policies. Siegel explained that epidemiologists often visualize disease prevention using a swiss cheese model wherein every layer of protection has holes, but, by layering protective measures, disease-causing pathogens can be prevented from spreading. “If you think about ventilation as one layer, it’s got a bunch of holes,” said Siegel. Without a mask or vaccination mandate, he added, “we’re relying on one layer, and we’re not doing everything we can to make sure that layer is as protective as it can be.” U of T’s vaccine and mask mandates have been paused since July 1.

Furness believes that many holes exist in the university’s HVAC systems. “Any building that was built before COVID is going to be built to sort of a normal standard,” said Furness. “Legacy buildings like Hart House or Trinity College or Victoria College are on the university steam heating system. There’s a whole integrated network of steam pipes providing heat, so there is no systematic forced air.”

Despite setting stringent standards for classrooms, U of T has not set similar standards for other areas of buildings, such as offices, entryways, and common spaces. The university’s rationale is that such areas are not as likely to pose the same risk of transmission as crowded classrooms. 

However, according to Furness, this oversight presents a problem. Describing buildings as “dynamic systems” with air constantly flowing between classrooms and the surroundings, he explained that students spend significant time in spaces other than classrooms. “We haven’t addressed ventilation in a lot of [non-classroom] spaces,” he said. 

According to Siegel, even the ventilation measures that the university implemented in classrooms are not necessarily adequate. He explained that the air filters that are used in centralized filtration at UTSG have a very high initial filtration rate, but often degrade quickly. 

Siegel added that portable air filtration systems, such as those used in classrooms, also pose a number of challenges. He noted that such filters offer localized coverage, but they don’t necessarily protect the entire space. Filter noise, Siegel continued, can also lead some people to turn the units down or off. 

Although the university claims to be on top of maintaining filtration units, Siegel cautions that there may simply be too many units for the administration to maintain and monitor. “I’m going to guess we’re going to be seeing [unit] removal rates that are a factor of two or three less than the calculations suggest in a lot of places,” said Siegel. 

U of T response

In a statement to The Varsity, a U of T spokesperson affirmed that its ventilation and filtration measures “impact all areas of buildings including hallways, meeting rooms and common spaces” and that “all systems are regularly inspected and maintained according to system specifications and best practices.”

According to the U of T spokesperson, supplemental air purifiers are being used in classrooms that do not meet the six ACH threshold. The spokesperson added that the air purifiers were most recently inspected by a third-party expert in August.

The spokesperson explained that the upgrades to a building’s ventilation system are in part determined by the condition of the particular building: “For example, in heritage buildings, renovations and system changes may not be allowed.”

There are 86 heritage buildings on U of T campuses, only six of which are not located at the UTSG campus. The university works with the City of Toronto to ensure the preservation of these buildings and must consider a variety of guidelines when implementing any changes or alterations to these buildings.

The spokesperson concluded that, while the university has paused its mask mandate, students are encouraged to wear masks in crowded spaces and respect one another’s decision to do so.

With files from Syeda Maheen Zulfiqar.