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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 migrate into buildings from contaminated groundwater or soil. Vapor intrusion can cause potentially unhealthy levels of hazardous substances in indoor air.

2009 draft guidance online

In 2009, Ecology developed a draft technical guidance manual that 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 The draft guidance also recommends ways to protect people in impacted buildings. Ecology is reviewing the draft guidance, and plans to develop updated guidance during the next several years.

2017 draft memo

In August 2017, we released the draft guidance memo, Petroleum Vapor Intrusion (VI): Updated Screening Levels, Cleanup Levels, and Sampling Considerations (Implementation Memo No. 18)

Key Ecology documents

EPA documents

EPA guidance documents related to vapor intrusion:

For questions or to submit comments: 

Mark Gordon, P.E.
Department of Ecology – Toxics Cleanup Program
P.O. Box 47600
Olympia, WA  98504-7600
(360) 407-6357 

This page last updated August 7, 2017