As modern life increasingly shifts toward indoor environments, the quality of the air we breathe within the walls of our homes, offices, and classrooms has become a focal point for public health researchers. Statistics indicate that the average person typically spends upwards of 80% of their time indoors. While it is common to assume that four walls and a roof provide a sanctuary from the smog and haze of the outside world, new research from the University of Utah suggests that the reality is far more complex. The study highlights that indoor air quality is not a static condition but a dynamic one, dictated by a building’s age, its proximity to pollution sources, and, perhaps most critically, the specific design of its heating, ventilation, and air conditioning (HVAC) systems.
The research, conducted by an interdisciplinary team at the University of Utah, utilized the Salt Lake City campus as a sprawling "living laboratory." By combining the expertise of the College of Engineering, the Department of Facilities Management, and occupational and environmental health researchers, the team sought to understand the invisible exchange between the outdoor atmosphere and indoor spaces. Their findings offer a nuanced look at how different types of particulate matter—ranging from the heavy dust of desert storms to the microscopic soot of wildfires—interact with commercial ventilation technologies.
While the study concluded that indoor air quality across the campus was generally high, it identified a significant vulnerability during wildfire season. The research demonstrated that certain energy-saving HVAC configurations can inadvertently pull fine particulate pollution, known as PM2.5, into buildings, even while successfully blocking other types of pollutants like winter inversion particles and wind-driven dust.
The Campus as a Living Laboratory
The decision to use the university campus for the study provided the researchers with a unique opportunity to observe a wide array of building styles and mechanical systems in a controlled yet real-world setting. The University of Utah’s main campus is a microcosm of urban architecture, featuring everything from historic structures with older ventilation setups to state-of-the-art facilities equipped with modern energy-efficiency technologies.
"Our buildings are big and they’re complicated, and oftentimes they’ve been added onto and integrated with different kinds of systems," said Kerry Kelly, a professor of chemical engineering who oversaw the research. Kelly noted that while the complexity of these systems makes management a significant challenge, the data gathered by the team suggests that the issues identified are fundamentally solvable. The study suggests that through a combination of mechanical adjustments and simple interventions, such as the use of portable air filters, the risks posed by outdoor pollutants can be mitigated.
The project relied on a dense network of low-cost, wirelessly connected sensors. These devices were deployed across 17 indoor locations and two outdoor stations to capture a comprehensive picture of air movement. The goal was to characterize the behavior of indoor air quality during three specific types of high-pollution events common to the Intermountain West: dust storms, winter inversions, and wildfire season. Each of these events presents a different chemical and physical profile of PM2.5, and they occur at different times of the year, providing a robust dataset for the researchers to analyze.
Tristalee Mangin, a graduate student in chemical engineering and the study’s lead author, explained the methodology used to track the infiltration of these particles. "We look at the ratio of the indoor particulate matter measurements to that of the outdoor particulate matter measurements," Mangin said. "The closer that value gets to one, which means more of the particulate matter is going to be sourced from outdoors versus indoor sources." By analyzing these ratios across different groupings of HVAC types, the team was able to pinpoint exactly which systems were most susceptible to outside air quality fluctuations.
How Smoke Differs from Dust and Inversions
