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Vapor Intrusion Resources For Environmental Professionals

Screening for the vapor intrusion (VI) pathway must be conducted at every contaminated site in Wisconsin. The need to investigate VI is elevated when screening indicates the potential for VI is present, especially when trichloroethylene (TCE) is present due to its potential for acute (short-term) health risks. Mitigation is the process of interrupting the VI exposure pathway such that the vapors no longer affect occupants. Mitigation is not a form of remediation.

This webpage provides resources to help environmental consultants screen the vapor pathway, assess vapor risk and investigate and mitigate vapor intrusion at specific buildings.

January 2021 - The Interstate Technology & Regulatory Council (ITRC) published a comprehensive web-based series of technical resources for VI mitigation. An overview of mitigation options and key considerations, from the conceptual site model to an exit strategy, are included. See "ITRC guidance" under the "Guidance and Forms" tab below.

Guidance On Addressing Vapor Intrusion

Vapor migration is a contaminant pathway that needs to be evaluated like other pathways. Its evaluation is required by Wis. Adm. Code NR 716.11(5)(a), (b), (g) and (h).

Primary DNR VI Guidance
  • Addressing Vapor Intrusion at Remediation and Redevelopment Sites in Wisconsin (RR-800) - provides the framework for responsible parties and consultants to screen, investigate, remediate and mitigate the vapor pathway at contaminated sites in order to satisfy the requirements for case closure. Guidance on vapor migration within utility conduits, vapor intrusion from utilities and how to investigate this preferential pathway has been added to RR-649 (see below).
Supplemental DNR VI Guidance
DHS Guidance
EPA Guidance
ITRC Guidance

Screening Levels

Wisconsin Vapor Quick Look-Up Table Indoor Air Vapor Action Levels (VALs) And Vapor Risk Screening Levels (VRSLS) (RR-0136)

Indoor air vapor action levels (VALs) are based on U.S. Environmental Protection Agency (U.S. EPA) Regional Screening Level Tables, applying a 1 x 10E-5 excess lifetime cancer risk or a hazard index of 1 for non-carcinogens. The Wisconsin Vapor Quick Look-Up Table Indoor Air VALs and VRSLs (RR-0136) includes volatile organic compounds (VOCs) that are frequently encountered on remediation sites. The table is updated periodically, primarily when the U.S. EPA updates its tables based on inhalation toxicity data.

The Wisconsin Vapor Quick Look-Up Table Indoor Air VALs and VRSLs (RR-0136) - (updated August 2023) provides:

  • Indoor air VALs for VOCs frequently encountered on remediation sites;
  • Sub-slab VRSLs for three building categories (residential, small commercial and large commercial/industrial) for these common VOCs;
  • A link and instructions for using the U.S. EPA's Vapor Intrusion Screening Level (VISL) Calculator to determine VALs and VRSLs for other chemicals;
  • Attenuation factors for five screening media (crawl space, sub-slab, soil gas, groundwater and sanitary sewer gas);
  • Instructions and a formula for calculating groundwater VRSLs; and
  • A link, instructions and a formula for converting units of data [e.g., parts per million by volume (ppbV) to micrograms per cubic meter (µg/m3)].

Although the VISL Calculator began reporting results with three significant figures in 2020, the DNR continues to apply VALs and VRSLs with two significant figures. This resulted in minor updates to some VALs and VRSLs on the table beginning with the September 2021 publication. Any value on the table that is updated from the previous version is bolded.

History of Changes To VALs, VRSLs and Attenuation Factors For Common VOCs

Wisconsin's VALs and VRSLs have changed over time because of updates to U.S. EPA's risk calculations and default attenuation factors. This table, Guidance: History of Changes to VALs, VRSLs and Attenuation Factors for Common VOCs (RR-0137), is a quick reference to the historical values with dates when changes occurred, intended to help users understand the basis for past decisions at sites.

Using U.S. EPA's Vapor Intrusion Screening Level (VISL) Calculator To Determine Wisconsin VALs and VRSLs

The VISL and VISL User Guide may be used to calculate VALs for compounds not listed in the Wisconsin Vapor Quick Look-up Table Indoor Air VALs and VRSLs (RR-0136). The user should:

  1. Adjust the default hazard quotient to 1, the default target risk to 1x10E-5 and choose the risk scenario (residential or commercial).
  2. Select one or more individual chemicals in the selection field.

The calculator will provide the target indoor concentrations for the carcinogenic and noncarcinogenic endpoints for the individual chemical(s) selected using a default attenuation factor of 0.03. The VAL is equal to the lesser of the two values rounded to two significant figures. More detailed instructions are listed on the Wisconsin Vapor Quick Look-Up Table Indoor Air VALs and VRSLs (RR-0136).



The DNR partners with the Wisconsin Department of Health Services (DHS) and local health departments regarding short-term (acute) and long-term (chronic) risks to human health related to vapor intrusion, as well as determining appropriate immediate and interim recommendations (e.g., ventilation, mitigation) at affected sites. DHS and local health departments assist the DNR, responsible parties and environmental consultants with health risk communications, including supportive literature. 

  • DHS fact sheet specific to the health concerns of trichloroethylene (TCE) in the air of buildings where the chemical may have unexpectedly traveled (e.g., residences, schools, daycares, businesses that do not use TCE):

Community Outreach

Community outreach

An effective outreach strategy that anticipates the needs and concerns of affected property owners and the community at large is important when vapor intrusion is involved. When citizens are well-informed about the issues surrounding a site, their questions and concerns can be more effectively addressed. Early two-way communication is essential for a successful investigation and mitigation effort. The following model letters and fact sheets are available for use with your outreach communications.

Template/Model Letters

The DNR created template letters to help environmental professionals communicate vapor intrusion investigations with affected property owners in plain, easily understood language. Because of the complex nature of vapor intrusion investigations, it is not possible to create a template letter for every situation. These template letters are yours to use as you see fit, in whole or in part.

Request For Access To Sample
Sample Results
Request To Install Mitigation System

DNR Fact Sheets

These fact sheets are intended to help environmental consultants and responsible parties communicate critical information about the vapor intrusion pathway to affected property owners. The fact sheets can be used in conjunction with template letters or as stand-alone documents.  When planning an outreach strategy, decide which fact sheets and other tools best support the information you want to communicate to neighbors and other interested parties.

DNR videos

Like the fact sheets above, these videos are intended to help environmental consultants and responsible parties communicate critical information about the vapor intrusion pathway to affected property owners. These videos should be used in conjunction with fact sheets or other documents.


DNR Webinar Training

The Remediation and Redevelopment Program provides web and teleconference-based training sessions that cover a variety of technical and policy issues. Visit the RR Program training library to access the presentations and find vapor intrusion-related topics.

2014 Vapor Intrusion Outreach "Toolkit"

Anticipating the needs and concerns of affected property owners and the community at large is critically important whenever vapor intrusion is involved. Clear and effective communication with them should be one of the goals of any outreach plan. To help with those efforts, the DNR created a comprehensive toolkit of vapor intrusion communication materials to increase the consistency and effectiveness of communications between responsible parties and the public.

2011 Vapor Intrusion Issues in Wisconsin - FET Webinars

In March 2011, staff from the RR Program participated in two Federation of Environmental Technologists (FET) webinars about vapor intrusion issues in Wisconsin. The agenda, PowerPoint presentation slides and videos of the presentations are available below.

2011 Webinar PowerPoint slides
2011 Webinar Presentation videos

Other Resources


Workshops and Conferences


Department of Defense Environmental Security Technology Certification Program (ESTCP)
Naval Facilities Engineering Command (NAVFAC)
American National Standards Institute (ANSI) / American Association of Radon Scientists and Technologists (AARST)
American Petroleum Institute
Electric Power Research Institute (EPRI)


Interstate Technology & Regulatory Council (ITRC)
Strategic Environmental Research and Development Program (SERDP) and Environmental Security Technology Certification Program (ESTCP)



If you have general questions, contact Jennifer Borski or Jim Walden.

For site-specific questions, please contact a DNR regional project manager. To determine which project manager you should contact, please see the RR Program's regional map.

Regional Vapor Intrusion Experts

DNR Region Contact Person
Northeast (NER) Josie Schultz
Northern (NOR) Grant Neitzel
South Central (SCR) Cindy Koepke
Southeast (SER) Jane Pfeiffer, Connor Mulcahy, Joe Martinez
West Central (WCR) Candace Sykora