Vapor Intrusion
The migration of volatile chemical vapors from contaminated soil or groundwater into overlying buildings through cracks and openings.
Vapor intrusion is the process by which volatile organic compounds (VOCs) from contaminated soil or groundwater migrate upward through the soil and enter overlying buildings through cracks in foundations, utility conduits, and other openings. At LUST sites, petroleum vapors containing benzene and other BTEX compounds can accumulate in indoor spaces, creating potential health risks for building occupants.
The EPA has recognized vapor intrusion as a significant exposure pathway at petroleum-contaminated sites. In 2015, the agency released technical guidance for evaluating petroleum vapor intrusion, including screening criteria based on the distance between contamination and buildings, depth to groundwater, and bioattenuation factors that reduce vapor concentrations as they migrate through clean soil.
Assessment of vapor intrusion risk typically involves sub-slab soil gas sampling, indoor air monitoring, and groundwater vapor analysis. If unacceptable indoor air concentrations are detected, mitigation measures may include sub-slab depressurization systems (similar to radon mitigation), building sealing, or addressing the source contamination through remediation. Properties near LUST sites should evaluate vapor intrusion potential during environmental due diligence.
Related Terms
A group of volatile organic compounds commonly found in petroleum products and frequently detected at LUST sites.
Benzene ContaminationEnvironmental pollution by benzene, a carcinogenic compound found in gasoline and commonly detected at LUST sites.
Groundwater ContaminationThe pollution of underground water sources by petroleum products or hazardous substances from leaking USTs or other sources.
Phase I Environmental Site Assessment (ESA)A report assessing the likelihood of contamination on a property, commonly required during real estate transactions.