In general, we spend 80% of our time indoors, where the quality of the air we breathe depends on the age and type of building we occupy, as well as internal pollution and sources of outdoor pollution. But also playing an important role is the type of HVAC system used to heat, ventilate and cool the building, according to a new research from the University of Utah.
Using the Salt Lake City campus as a living laboratory, the Faculty of Engineering was associated with the management of occupational and environmental health facilities and researchers to explore whether outdoor air pollution affects the quality of the inner air. They discovered that the quality of the inner air on the campus was generally good. However, depending on the HVAC system of a building, the contamination of fine particles or PM2.5, of the smoke of forest fires can infiltrate buildings, while the contamination associated with powder events and winter investments remains out.
The study found that the problem lies in HVAC’s commercial systems that use economizers on the air side. Using special provisions of ducts and shock absorbers, this technology reduces the use of energy by extracting air from the outdoors when temperature and humidity levels are optimal, such as cold summer and autumn mornings. This helps with energy efficiency, but if the air is smoked that day, the system could attract particle contamination and some particles exceed filters, according to the chemical engineering professor Kerry Kelly, who supervises the investigation.
Campus as a laboratory
“Our buildings are large and complicated, they have often added and integrated with different types of systems,” Kelly said. “So I think the administration is a challenge, but the good thing is that it is a very soluable problem. Even simple solutions such as portable air filters do a great job.”
The current project deployed low -cost connected sensors in 17 interior and exterior locations in an effort to characterize what happens with the quality of the inner air when particle pollution rises during dust storms, winter investments and the forest fire season, which have different types of PM2.5 and occur at different times of the year.
“We observe the relationship of interior particles measurements to those of the measurements of outdoor particles. The more that value is closer to one, which means that more of the particles will be obtained from outdoor sources versus interior sources,” said study leader Tristalee Mangin, a student graduated in chemical engineering. “We observed those proportions and then we did analysis based on the different groups of HVAC types.”
How smoke differs from dust and investments
The smoke of the forest fire had four or five times more infiltration of PM2.5 in buildings than the contamination of wind and wind events driven by the wind. However, the overcoming of international health patterns only occurred in ventilated buildings with economizers on the air side and were still very rare.
The team used small devices designed by Pierre-Emmanuel Gaillardon, professor of electrical and computer engineering, and was marketed through a startup or called Tellus. The cost per device was only $ 450, much less than the compliance equipment would cost. They settled on the walls at the height of the breathing in a variety of buildings extended mainly around the main campus.
According to its findings, the outdoor pollution that arises from dust and wind bluked by the wind did not have much effect on the quality of the inner air, regardless of the HVAC system. This is probably the result of the nature of PM2.5 associated with these contamination events.
The dust particles are typically larger and heavier than smoke particles, so they tend to fall from the air and are trapped in filters. Investment particles are a more complicated story.
“It has to do with the thermodynamics of the particles that are in investment. The subject of Utah particles is mainly ammonium nitrate, as 60% of our particles,” Kelly said. “At interior temperatures and relative humidities, these particles become a gaseous phase. During an investment, most of the things that are a particle outside is not a particle when it enters.
Research continues to find solutions
This document is based on an 18 -month study window that ended in April 2024, but the investigation is ongoing and the monitors remain active and visible. A statement on the investigation and how it is funded by a subsidies Seed2soil and SCIF is published next to the devices.
In addition to shedding light on the strengths and weaknesses of HVAC systems to avoid pollution, the findings are expected to help the construction managers of the campus to create operational adjustments to maintain good interior air quality, particularly during the forest fire season. However, the approximately 18 million square feet of the construction space of the campus exhibit a great variety that defies a uniform approach, according to the co -author Sean Nielson, an engineer of the Sustainability and Energy Group of facilities management.
“Each building and system has unique characteristics,” said Nielson. “Looking for buildings and systems individually is something that we will consider in the future and see what we can do to modify that system.”
It will not be a simple matter of closing shock absorbers in smoked days, but rather adjust them based on the specific needs of private buildings.
“It still has minimal code requirements for a certain amount of exterior air that must be provided,” said Nielson. “A main reason for outer air is to dilute and eliminate interior pollutants. Finding the ideal balance between the outer air and the internal recirculated of the air is difficult due to the high amount of variables. The application of the MERV air filtration of greater rating is a tool that often works to improve the air for many applications, but there are limitations in what contaminants can be filtered effectively and how they can be applied to the existing equipment.