When wildfire smoke blanketed Toronto last week, two University of Toronto chemical engineering students turned a real-world environmental event into an opportunity to better understand how smoke affects indoor air quality.
Working with Professor Arthur Chan‘s Environmental Organics Laboratory, incoming fourth-year student Jenn Xu and incoming third-year student Katerina Sajeniouk deployed and calibrated air quality sensors throughout the Wallberg Building to measure particulate matter (PM2.5) levels during the wildfire smoke event.
From July 15 to 20, Xu led the deployment of approximately six PurpleAir sensors in classrooms, laboratories and common areas throughout the building. The sensors monitored indoor particulate matter levels and compared them with outdoor conditions and recommended “safe” air quality levels.
“My research is generally about measuring indoor air quality and pollutants that can affect both human health and artefacts,” says Xu. “With the timing of the wildfires, it made sense to measure air pollutants, particularly particulate matter (PM2.5), which increases significantly with wildfire smoke and can be hazardous to human health.”
The duo strategically selected monitoring locations based on conditions observed throughout the building. Some professors requested sensors in their offices and laboratories, while other locations were chosen because of noticeable smoke odours or differences in ventilation.
“On the first day of the wildfires, the air outdoors was so polluted with wildfire smoke that it looked like a yellow/orange filter was put over everything,” Xu recalls. “There were many rooms that noticeably smelled like burning wood, which was cause for concern.”
While Xu focused on collecting measurements, Sajeniouk ensured the data would be accurate by calibrating the PurpleAir sensors against a reference-grade air quality monitor.
PurpleAir sensors are widely used because they are compact and low-cost, making them practical for deployment in many locations. However, calibration is essential to ensure the measurements accurately reflect real-world conditions.
“Calibration is what turns a raw signal from an inexpensive sensor into a number people can actually trust and act on,” says Sajeniouk. “Air quality data is often used to make real decisions, so if the underlying sensor data is inaccurate, those decisions could be wrong or even harmful.”
To improve accuracy, Sajeniouk co-located the PurpleAir sensors with a 5030i SHARP Monitor for approximately one week, allowing her to develop correction factors that aligned the lower-cost sensors with reference measurements. The process also highlighted the challenges of accounting for factors such as humidity and collecting enough data across different environmental conditions to produce reliable results.
Chan says the project demonstrates the value of connecting classroom learning with real-world environmental challenges.
“Engineering and chemistry aren’t concepts buried in textbooks or lectures—they surround us every day,” says Chan. “The course project in CHE230 is driven by students’ curiosity. We encourage them to ask questions, develop hypotheses and make measurements to answer their own questions.”
The recent wildfire smoke event provided an ideal opportunity to apply those skills to a timely public health issue.
“This summer, many people have been asking how the air quality is inside the places where we live and work, and whether we’re safe when we stay indoors,” says Chan. “With these sensors, we had the perfect opportunity to answer those questions.”
Chan says projects like this also complement government air quality monitoring by providing localized, real-time measurements, particularly indoors.
“Government air quality alerts are incredibly valuable for helping people plan their activities and limit their exposure,” he says. “Because these sensors are relatively inexpensive, we can deploy them ourselves, collect data in real time and even measure the air people are actually breathing indoors. That allows us to assess how well ventilation systems and air cleaners are working during wildfire smoke events.”
Beyond collecting data, the project gave both students the opportunity to apply concepts from their chemical engineering studies to a timely environmental challenge.
“It has been really interesting monitoring air quality in real-world scenarios, particularly with this wildfire season,” they say. “Being able to draw from what we’ve learned in the classroom to an unprecedented event happening in real time underscores the importance of what we do in school. It definitely puts into context what we’ve done in CHE230 and is a great tool for advisory purposes for both human and environmental health.”
The experience also reinforced the value of undergraduate research.
“Research experiences like this let us engage with open-ended problems that don’t have a clean answer,” they explain. “We had to troubleshoot unexpected sensor behaviour and make judgment calls with incomplete information. These are core skills for engineers but are hard to develop from coursework alone.”
The team will now compare indoor particulate matter concentrations with outdoor conditions and recommended safe levels to evaluate how effectively university buildings protect occupants during poor air quality events. They also hope to better understand how long it takes for indoor air quality to recover after outdoor conditions improve.
Chan says the research will continue beyond the Wallberg Building.
“We’re comparing air quality inside the Wallberg Building with outdoor conditions during these extreme smoke events,” he says. “That will help us provide guidance on whether indoor air quality remains safe during future wildfire events.” He adds that Xu will also deploy the sensors in museums and other public spaces to study indoor air quality in different environments.
For both students, the project has broadened their perspective on the role engineers can play in protecting public health.
“Working on this made it clear how much low-cost sensor networks can expand our understanding of air quality at a much finer scale, and how much careful engineering work goes into making that data trustworthy,” they say. “It’s shown us that engineers have a real role to play not just in building tools, but in making sure those tools produce data people can actually rely on for public health decisions.”