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Episodic Vapor Intrusion During Fall and Winter Intensive Sampling Events
Citation:
Williams, A., J. Zimmerman, B. Schumacher, C. Lutes, B. Cosky, K. Bronstein, R. Warrier, B. Thompson, L. Levy, AND C. Holton. Episodic Vapor Intrusion During Fall and Winter Intensive Sampling Events. ACE 2025 A&WMA 118th Annual Conference & Exhibition, Raleigh, NC, June 09 - 12, 2025.
Impact/Purpose:
There are multiple research needs to improve guidance on vapor intrusion (VI) from OLEM. Nearly all long term chemical VI research has been performed on residential structures, but large non-residential buildings are also affected and need to be characterized in the same manner. This research characterized VI in large buildings and studied controlling factors for a period of 15 months, gaining a better understanding of temporal variability VI controlling factors in residential and large buildings, and of VI during fall and winter events. These findings provide insight into how VI works in large buildings in a sub-artic climate and will be used to support updates of regional guidance documents, by OLEM to update their VI sampling guidance documents, and to better define and understand sampling methodology for large buildings in VI investigations. Program and regional Partners: Rich Kapuscinski, OLEM/OSRTI/ARD (recently retired); Henry Schuver, OLEM/ORCR/PIID; April Luke, OLEM/OEM/CCMAD; Lilian Abreu, R9/SEMD/CSCEB; Jessica Kidwell, R7/LSASD/ASB
Description:
This presentation examines short-term Vapor Intrusion (VI) temporal variability affected by seasons in volatile organic compounds (VOCs) measured in indoor air. Samples were collected concurrently from two buildings, a residential style office building (1600sqft), and a larger commercial sized church building (6000sqft). Each building was monitored for 6 months with onsite GC/MS that sampled multiple locations 2x-10x a day, as well as weekly passive and active sampling. VI indicators and tracers (I&T) including radon, differential pressure, indoor and outdoor temperature, heating, ventilation, and other environmental factors were monitored over the entire study at each building. The primary predictor variables that controlled the temporal variability at both buildings were generally the same despite structural differences. Weather fronts, pressure changes, and external temperature variations were the primary variables that generally led to temporal variability. As soil temperatures rose over the summer and were combined with the start of the heating season, a strong stack effect driving force resulted in both buildings having high levels of indoor air VOC concentrations in September, but each building also still experienced a winter driven stack effect series of peaks in December through February. Radon concentrations regularly shifted with VOC concentrations following similar patterns of highs and lows. Barometric pressure changes associated with the passage of weather fronts were also a consistent indicator of short term trend shifts in indoor air VOCs, but it’s resulting effect varied throughout the seasons. Results from this study clarified what factors influence seasonal and short-term temporal trends in indoor air VOC concentrations resulting from VI in commercial and residential-style buildings in a subarctic climatic zone.
