Vapor intrusion occurs when vapor-forming chemicals migrate from a subsurface source into an overlying building -- similar to radon gas seeping into homes.
Cal/EPA Vapor Intrusion Guidance Documents
- Flow Diagram of DTSC Documents Updated
- New! Advisory - Active Soil Gas Investigations (July 2015)
Jointly revised by DTSC, Los Angeles Regional Water Quality Control Board (LARWQCB), and San Francisco Regional Water Quality Control Board, this updated Advisory provides technically consistent approaches for collecting and analyzing soil gas samples. Data obtained from soil gas investigations can be used to identify the spatial distribution of volatile contamination at a site and assist in the evaluation of vapor intrusion. The 2012 revision incorporates all key elements from the LARWQCB’s 1997 "Interim Guidance for Active Soil Gas Investigation" and is a compilation of available information, knowledge, experience and best practices regarding soil gas sampling.
- New! Frequently Asked Questions (FAQ's) Updated (August 2015)
- New! Summary of Advisory Changes (2015)
- Final Guidance for the Evaluation & Mitigation of Subsurface Vapor Intrusion to Indoor Air (October 2011; also known as the Vapor Intrusion Guidance)
DTSC's Vapor Intrusion Guidance provides a stepwise and sometimes iterative process for the investigation of vapor intrusion and describes procedures for screening and site-specific evaluation of potential risks associated with this exposure pathway. Indoor air concentrations estimated from soil gas or groundwater concentrations by fate and transport models for vapor intrusion and/or measured indoor air concentrations are used in the assessment. Models for estimating indoor air concentrations include default attenuation factors for vapor migration from soil gas or groundwater to indoor air, and default and site-specific inputs to the U.S. EPA version of the Johnson and Ettinger vapor intrusion model.
- Summary of Changes Between Interim Final and Final Guidance
- Human Health Risk
- Screening-Level Model for Soil Gas Contamination Updated (December 2014)
- Screening-Level Model for Groundwater Contamination Updated (December 2014)
- Vapor Intrusion: Decision Framework for Testing Indoor Air & Overview of Sampling Procedures Presented at the February 2012 CUPA Conference
- Vapor Intrusion Mitigation Advisory, Revision 1 (October 2011)
Provides a framework that guides the reader through the decision process for 1) determining if mitigation is appropriate for the project site, 2) selecting a mitigation system that is protective of human health, and 3) ensuring that implementation is sustainable for the duration of mitigation. Emphasizes public participation and implementation considerations. Identifies likely technologies for vapor intrusion mitigation, but does not identify proven technologies.
- Summary of Changes Reflected in Revision 1
- Vapor Intrusion Public Participation Advisory (March 2012)
DT developed this Advisory to help determine and implement appropriate public participation coordination and activities at sites where a potential vapor intrusion risk has been identified. The Advisory is a companion document to DTSC's Vapor Intrusion Guidance and Vapor Intrusion Mitigation Advisory. In addition, the Advisory supplements DTSC's Public Participation and Procedures Manual.
- PT&R Guidance - Remediation of Chlorinated VOCs in Vadose Zone Soil (April 2010)
Presents an option for expediting and encouraging cleanup of sites with chlorinated volatile organic compounds (VOCs) in vadose zone soil. Applicable on a case-by-case basis to operating and closing hazardous waste facilities and Brownfields sites. Streamlines the cleanup process by: limiting the site-specific remedy evaluation to excavation/disposal and soil vapor extraction (SVE); providing guidance for selecting screening levels and cleanup goals; and providing resources that facilitate remedy implementation, documentation, and administrative processes.
Other Vapor Intrusion Resources