Modern life is defined by its interiority. On average, individuals spend approximately 80% of their lives inside buildings, whether for work, education, or rest. Within these enclosed environments, the quality of the air we breathe is often taken for granted, assumed to be a filtered sanctuary from the elements. However, the reality of indoor air quality is a complex tapestry woven from the age of the structure, the materials used in its construction, and the constant exchange between indoor and outdoor atmospheres.
New research from the University of Utah has shed light on a critical and often overlooked factor in this equation: the specific type of heating, ventilation, and air conditioning (HVAC) system used to manage a building’s climate. The study reveals that while these systems are designed for comfort and energy efficiency, certain configurations can inadvertently become conduits for outdoor pollutants, particularly during the increasingly frequent wildfire seasons that plague the American West.
The Campus as a Living Laboratory
To understand the nuances of air infiltration, researchers from the University of Utah’s College of Engineering turned their own campus into a massive, "living laboratory." This multi-disciplinary effort saw the College of Engineering team up with the university’s Facilities Management department and experts in occupational and environmental health. By using a diverse range of campus buildings—spanning various architectural eras and mechanical designs—the team sought to determine exactly how outdoor pollution events affect the air inside.
The findings were generally encouraging, suggesting that indoor air quality on the Salt Lake City campus remains high under most circumstances. However, the study identified a significant vulnerability regarding fine particulate matter, specifically PM2.5, during wildfire events. The research demonstrated that while pollution from winter inversions and wind-driven dust is largely kept at bay, wildfire smoke has a unique ability to penetrate certain types of buildings.
The discrepancy in how these pollutants behave is tied directly to the mechanical "lungs" of the buildings. Specifically, the study highlighted challenges associated with commercial HVAC systems equipped with air-side economizers.
The Efficiency Paradox: Air-Side Economizers
Air-side economizers are a staple of modern green building design. This technology is intended to reduce energy consumption by utilizing "free cooling." When the outdoor temperature and humidity reach optimal levels—such as on a crisp summer morning or a cool autumn afternoon—the system uses a series of ducts and dampers to draw in outdoor air rather than running energy-intensive mechanical cooling units.
While this is a boon for energy efficiency and sustainability goals, it creates a direct pathway for atmospheric contaminants. Kerry Kelly, a professor of chemical engineering who oversaw the research, explained that if the outdoor air is thick with smoke, these economizers can pull that particulate matter directly into the building’s circulation. Although the systems are equipped with filters, some of the finest particles from wildfire smoke manage to bypass these defenses and settle into the indoor environment.
"Our buildings are big and they’re complicated, and oftentimes they’ve been added onto and integrated with different kinds of systems," Kelly noted. This complexity makes the management of air quality a moving target. Despite the challenges, Kelly remains optimistic about the future of indoor air management. "I think the management is challenging, but the good thing is it is a very solvable problem. Even simple solutions like portable air filters do a great job."
