Modern office buildings are pumping out volatile chemicals to the surrounding environment at levels comparable to traffic emissions, according to researchers.
The study, at Purdue University in Indiana, found that a high-performance building with state-of-the-art air quality instrumentation and advanced automation continually released volatile organic compounds (VOCs) to the outdoor area. This made it likely to be an important contributor to the ‘VOC burden’ of the urban atmosphere, the team found.
VOCs include a wide range of chemicals, found in everything from paints to perfumes, fuels and refrigerants. While some have no known impact on health, some can cause irritation, and others have long-term health risks such as cancer.
“We traditionally think of filtering the outdoor air entering our buildings. Based on the findings of our study, we now need to consider cleaning the air leaving our offices, homes and schools to reduce VOC emissions to the outdoor environment,” said research leader Brandon Boor.
The research aimed to accurately measure VOCs in the air coming in and out of urban buildings, and to use the data to understand how human occupancy and building operation impact VOC transport between indoor and outdoor air. Boor said that the influence of air exchange between indoor and outdoor atmospheres on urban air pollution is still not well understood, and had not previously been fully explored before in a modern office building with a sophisticated ventilation system.
“A fundamental understanding of the fate and transport of urban air pollutants is important for developing mitigation strategies and policies that can improve urban air quality and reduce adverse impacts on human health and the climate,” Boor said. “Numerous studies have demonstrated the significant impact of traffic, industrial and biogenic emissions on urban air pollution. However, the influence of urban air pollutant interactions with buildings has often been overlooked.”
Modern public and commercial buildings are typically equipped with heating, ventilation and air conditioning (HVAC) systems to provide improved indoor air quality and thermal comfort. When urban air is mechanically circulated throughout buildings, its composition can change significantly due to interactions with HVAC components, indoor air, occupants and surfaces.
“Buildings account for a significant fraction of the land area in cities and provide a significant amount of occupied indoor space,” said Tianren Wu from the University of Cincinnati, first author on the study.
“To meet building ventilation and thermal comfort requirements, a substantial amount of air is actively exchanged between a building and its proximate urban atmosphere. This dynamic air exchange may have important implications for urban air quality due to both indoor-to-outdoor and outdoor-to-indoor transport and transformations of pollutants, especially in densely populated cities.”
Building materials, interior furnishings, and occupants and their activities – such as cooking, cleaning, and using consumer and personal care products – release a variety of gaseous and particulate contaminants, which can be directly exhausted into the urban atmosphere via a building’s HVAC system. Boor’s research found that indoor VOC concentrations are two- to 15-times higher than outdoors. Per unit area, the work found that building emissions of VOCs are comparable to traffic and industrial emissions.
The office used for the month-long research was Ray W Herrick Laboratories, a high-performance university building in central Indiana. The office is continuously mechanically ventilated by an independent air handling unit.
The field measurement campaign was carried out in winter. VOCs, ozone and fine particulate matter were measured, and the mechanical ventilation conditions of the building were monitored to quantify net emission rates from the office to the urban atmosphere. VOCs were measured in real-time at different locations throughout the HVAC system.
The team found the office to be a significant emission source of reactive monoterpenes and siloxanes to the outdoor environment. Siloxanes are widely used in deodorants, perfumes, lotions and hair care products. A recent study led by Purdue’s Nusrat Jung found everyday hair care routines release large amounts of siloxanes to outdoor air via bathroom exhaust, further demonstrating how buildings can impact outdoor air pollution.
“The building source-sink behaviour changed dynamically with occupancy and building ventilation conditions,” Boor said. “Our results demonstrate that buildings can directly influence urban air quality due to substantial outdoor-indoor air exchange.”
Boor said a greater focus is needed on removing VOCs in HVAC systems using carbon filters and other air cleaning technologies. Using consumer and personal care products with low VOC emissions could also help.
Researchers from Indiana University and RJ Lee Group also contributed to the study, which was published in Cell Reports Sustainability.
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