Vapor intrusion

When soil or groundwater is contaminated, potentially hazardous vapors may migrate into buildings. These volatile organic or inorganic compounds (or both) can potentially impact indoor air quality.

We provide guidance to help you investigate vapor intrusion concerns at your cleanup site and determine what to do about it. We've also linked to an important update: the 2015 changes in toxicity values and screening levels. You'll find links to Environmental Protection Agency guidance, too. 

Our state's vapor intrusion guidance was developed under Washington's cleanup law, the Model Toxics Control Act (MTCA).

Comment on new draft guidance through January 7, 2019

In 2009, we produced Draft Vapor Intrusion Guidance (Publication No. 09-09-047) to help site managers manage vapor intrusion pathways at cleanup sites. In November 2018, we released a new draft memo to supplement that guidance, and we invite you to comment on it. ​

Draft Vapor Intrusion (VI) Investigations and Short-Term Trichloroethene (TCE) Toxicity (Implementation Memo No. 22) provides recommendations for cleanup sites that are contaminated with trichloroethene (TCE).  Submit your comments through Monday, January 7, 2019, through our eComments page.

Graphic of two houses on top of soil and a groundwater plume of contamination.  Vapors from contaminated soil and groundwater are migrating through cracks into the homes.

This figure shows volatile chemicals migrating from contaminated soil and groundwater plumes into buildings. Chemicals are entering through cracks in the foundation and openings for utility lines. Atmospheric conditions and building ventilation are influencing vapor intrusion. Source: Environmental Protection Agency's vapor intrusion webpage, accessed October 2017.

What’s vapor intrusion?

Vapors from volatile organic compounds or inorganic compounds (or both) can migrate into buildings when the surrounding soil or groundwater is contaminated. This “vapor intrusion” can cause potentially unhealthy levels of hazardous substances in indoor air.

Guidance, screening levels, and other related vapor intrusion information