ABSTRACT
Vapor intrusion (VI) caused by releases of volatile chemicals from contaminated soil and/or groundwater is rapidly emerging as a serious concern with potentially significant impact on thousands of properties across the nation. Volatile chemicals such as trichloroethylene,perchloroethylene, and benzene may be released from contaminated soil and/or groundwater at properties such as existing or former gas stations, dry cleaners, and industrial facilities. These volatile chemicals may migrate through subsurface soils and into indoor air spaces of overlying structures similar to the way radon gas can seep into homes. The driving force can be convective (bulk flow) or diffusive (concentration) driving force and commonly enters via cracks or openings in the building floors or walls. These vapors can also migrate as a result of pressure differences between the building's interior (lower pressure) and exterior. This condition can create a negative pressure within the structure that effectively draws the vapors into the building. Thus, contaminated groundwater can pose a potential VI threat to inhabitants of nearby buildings and/or structures.
