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Final Program


Final Program

ACE 2025

WAST

Vapor Intrusion and Methane Hazards

Pulsed Vapor Intrusion During Fall and Winter Intensive Sampling Events

Tuesday, June 10, 2025
1:50pm – 2:10pm ET
Location: 306C
Abstract Description: Short-term temporal variability of vapor intrusion (VI) of volatile organic compounds (VOCs) is affected by seasonal changes. To examine this variability, samples were collected concurrently from two buildings, a residential-style office building (140 m2 [1600 ft2]), and a larger-sized commercial church building (557 m2 [6000 ft2]) in Fairbanks, Alaska. Each building was intensively monitored 2 to 10 times a day at multiple locations within the buildings for 6 months with onsite gas chromatography/mass spectrometry (GC/MS), as well as weekly passive and active VOC sampling. Over the entire study at each building, VI indicators and tracers were monitored including radon, differential pressure, indoor and outdoor temperature, heating, ventilation, and other environmental factors.

The primary predictor variables that controlled the temporal variability included weather fronts, pressure changes, and external temperature at both buildings, despite structural differences. As soil temperatures rose over the summer and were combined with the start of the heating season, a strong stack effect occurred pulling air up and into the buildings due to differences between the indoor and outside temperatures. Higher levels of indoor air VOC concentrations were observed in both buildings in September, and again in December through February owing to a winter driven stack effect exhibited as a series of peaks. Radon concentrations indoors regularly shifted with indoor VOC concentrations following similar patterns of high and low outdoor temperatures. Barometric pressure changes associated with the passage of weather fronts were also a consistent indicator of short-term trend shifts of indoor air VOC concentrations, but its resulting effect varied throughout the seasons. Results from this study better characterize factors influencing seasonal and short-term temporal trends in indoor air VOC concentrations resulting from VI in a church and a residential-style building in a subarctic climatic zone.