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Toxics Cleanup Program

What is vapor intrusion?

Migration of Soil Vapors to Indoor Air
This figure depicts the migration of volatile chemicals from contaminated soil and groundwater plumes into buildings. Volatile chemicals are shown to enter buildings through cracks in the foundation and openings for utility lines. Atmospheric conditions and building ventilation are shown to influence vapor intrusion.

Vapor Intrusion; US Environmental Protection Agency.  Accessed July 2016

Vapor intrusion occurs when vapors from volatile organic and/or inorganic compounds seep into buildings from contaminated groundwater or soil. Vapor intrusion can cause potentially unhealthy levels of hazardous substances in indoor air.

Draft Guidance

Ecology’s developed draft technical guidance, which provides techniques for evaluating whether vapor intrusion could contaminate indoor air. The draft guidance also recommends ways to protect people in impacted buildings.

Ecology is reviewing and updating the draft guidance, and will work to develop new guidance during the next several years.

Key Ecology documents

EPA documents

EPA guidance documents related to vapor intrusion:


Mark Gordon 
(360) 407-6357

This page last updated July 26, 2016