Vapor intrusion

When soil or groundwater is contaminated, potentially hazardous vapors can 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).

Listening session for draft Memo No. 22

On December 17, 2018, we held a listening session on draft Implementation Memo No. 22 regarding short-term trichloroethene (TCE) toxicity from vapor intrusion. The listening session provided participants an opportunity to ask questions and give feedback on this document. Read the December 2018 listening session summary and presentation slides.

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