When soil or groundwater is contaminated, potentially hazardous vapors can migrate into buildings. These volatile organic or inorganic compounds (or both) can impact indoor air quality. This “vapor intrusion” can cause unhealthy levels of hazardous substances in indoor air. We provide guidance to help you investigate vapor intrusion concerns at your cleanup site and determine what to do about it.
Vapor Intrusion guidance and screening levels
The state's vapor intrusion guidance was developed under Washington's cleanup law, the Model Toxics Control Act (MTCA). It explains how to investigate and manage potential vapor intrusion concerns.
- Guidance for evaluating vapor intrusion in Washington state: Investigation and remedial action (updated March 2022).
- Evaluate whether vapor intrusion could contaminate indoor air at your site.
- Find recommendations for protecting people who live or work in impacted buildings.
- Focus on trichloroethylene (TCE) in residential indoor air (September 2019)