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 page provides resources to help environmental consultants screen the vapor pathway, assess vapor risk and, where necessary, investigate and mitigate vapor intrusion at specific buildings. General information about vapor intrusion for property owners, tenants and the general public is available on the Vapor Intrusion page.
January 2021 - The Interstate Technology & Regulatory Council (ITRC) published a comprehensive web-based series of technical resources for VI mitigation. This document provides an overview of mitigation options and key considerations, from the conceptual site model to an exit strategy. 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
- Guidance for Documenting the Investigation of Human-made Preferential Pathways Including Utility Corridors (RR-649) – focuses on vapor migration within utility conduits, vapor intrusion through plumbing features and the potential for leaks in compromised utilities. The guidance also provides a sanitary sewer gas screening level (SSGSL), suggests sample nomenclature for vapor samples and includes discussion on the preferential migration of contaminated groundwater, soil or surface water in human-made features. (updated June 2021)
- DNR Case Closure Continuing Obligations: Vapor Intrusion (RR-042) - helps responsible parties and environmental consultants determine which vapor intrusion continuing obligations should be selected when preparing for site closure and completing the Case Closure Request (Form 4400-202).
- Sub-slab Vapor Sampling Procedures (RR-986) - provides a detailed description of materials, methodology, sample frequency and report results for collection of sub-slab vapor samples.
- Maintenance Plans for Vapor Mitigation Systems/Vapor Intrusion Response Actions (RR-981) - an addendum to RR-606 and provides a checklist of items to address in a maintenance plan for a variety of vapor mitigation responses.
- Vapor Mitigation System Inspection Log (Form 4400-321) - fillable form created in October 2020 and crafted after the example in Appendix G of publication RR-800. The form allows site-specific photos of system components to be added and allows for more than one of the same components (e.g., drop points, fans). This form replaces form 4400-305 for maintenance plans for vapor mitigation systems, referenced in RR-981.
- Vapor intrusion health hazards
- TCE in the Air or TCE en el aire (Spanish version) - The Wisconsin Department of Health Services (DHS) fact sheet specific to the health concerns of trichloroethylene (TCE).
- Radon Mitigation (Reduction): Wisconsin Certified Radon Mitigation Contractors - Contractors on this list have passed national proficiency standards for mitigating (reducing) radon in buildings. The DNR strongly suggests that vapor intrusion mitigation be performed by contractors who have been certified by the National Radon Proficiency Program (NRPP).
- EPA Vapor Intrusion
- Technical Guide for Assessing and Mitigating the Vapor Intrusion Pathway from Subsurface Vapor Sources to Indoor Air - June 2015
- Technical Guide for Addressing Petroleum Vapor Intrusion at Leaking Underground Storage Tank Sites - June 2015
- Petroleum Hydrocarbons And Chlorinated Hydrocarbons Differ In Their Potential For Vapor Intrusion – Informational Paper
- Indoor Air Vapor Intrusion Mitigation Approaches
- Passive Samplers for Investigation of Air Quality
- ITRC Website, Guidance & Documents – search “vapor intrusion”
- ITRC's Vapor Intrusion Pathway: A Practical Guide
- Petroleum Vapor Intrusion: Fundamentals of Screening, Investigation, and Management - a link to the webinar on this guidance is available in the "Other resources" tab
- ITRC’s Technical Resources for Vapor Intrusion Mitigation (VIM) – Dec. 2020 – This comprehensive, web-based document includes an interactive directory with 10 fact sheets, 16 technology information sheets and four checklists.
WI Vapor Quick Look-Up Table Of Indoor Air Vapor Action Levels (VALs) And Vapor Risk Screening Levels (VRSL)
Indoor air vapor action levels (VALs) are based on U.S. EPA's Regional Screening Level Tables, applying a 1 x 10-5 excess lifetime cancer risk or a hazard index of 1 for non-carcinogens. The Quick Look-Up Table 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 for Indoor Air VALs and VRSL (RR-0136 - updated Sept. 2021) provides:
- indoor air VALs for VOCs frequently encountered on remediation sites;
- sub-slab vapor risk screening levels (VRLs) 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 U.S. EPA’s 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, most notably to values listed in ppbV. Any value on the table that is updated from the previous version is bolded on the May 2021 version. For example, the sub-slab VRSL for tetrachloroethylene (PCE) at a small commercial facility is bolded because it was updated from 6,000 µg/m3 to 5,800 µg/m3.
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) - updated Sept. 2021), 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 WI VALs and VRSLs
The U.S. EPA Vapor Intrusion Screening Level Calculator (VISL) and VISL User Guide may be used to calculate VALs for compounds not listed in the WI Vapor Quick Look-up Table. The user should:
- Adjust the default hazard quotient to 1, the default target risk to 1x10-5 and choose the risk scenario (residential or commercial).
- 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 pages 2 and 3 of the Wisconsin Vapor Quick Look-Up Table (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 developed a fact sheet specific to the health concerns of trichloroethylene (TCE):
- Letter from DHS to DNR with recommended time frames and response actions at vapor intrusion sites:
- Letter from DHS to the DNR:
- For more information about vapor intrusion and health, visit the DHS website or view their vapor intrusion fact sheet:
- Study referenced in DNR’s April 6, 2021, letter to Responsible Parties:
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.
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.
- Vapor Intrusion Investigation - Information Sheet for Neighbors (RR-067) or Investigación de intrusión de Vapor — Hoja de Información para Vecinos - (RR-067a: Spanish version) A cover sheet to assist RPs or the state in access request to offsite properties. Provides property owners information on who is involved, how they are connected and who to contact with questions.
- Introduction to Vapor Intrusion Issue in Neighborhood (RR-958) - an introductory letter from a responsible party regarding vapor intrusion investigation and/or cleanup in a neighborhood.
Request For Access To Sample
- First Request for Access to Sample for Vapor Intrusion (RR-956) - a template letter seeking permission to gain property access to test for vapor intrusion.
- Second Request for Access to Sample for Vapor Intrusion (RR-957)- a template letter seeking permission to gain property access to test for vapor intrusion if the first letter yields no response.
- Access Agreement to Sample for Vapor Intrusion (RR-976) - a template access agreement to formally allow access for vapor intrusion sampling.
- Vapor Intrusion Sample Results No Detection (RR-960) - a template letter for a responsible party to send to a homeowner after vapor intrusion sampling does not detect the presence of the contaminant of concern.
- Vapor Intrusion Sample Results Below Screening Level (RR-961) - a letter for a responsible party to send to a homeowner when vapor intrusion sample results detect the contaminant of concern below screening level.
- Vapor Intrusion Sample Results Above Screening Level (RR-962) - a template letter for a responsible party to send to a homeowner when the contaminant of concern is detected above applicable screening levels.
Request To Install Mitigation System
- First Request for Vapor Intrusion Mitigation System Installation (RR-959) - a template letter to send to the homeowner to suggest installing a vapor intrusion mitigation system.
- Second Request for Vapor Intrusion Mitigation System Installation (RR-985) - a template letter to send to the homeowner to suggest installing a vapor intrusion mitigation system if the first attempt yields no response.
- Access Agreement for Installation of Vapor Mitigation System (RR-984) - template access agreement to formally allow for access and installation of a vapor intrusion 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.
- What is Vapor Intrusion (RR-892) - This fact sheet defines vapor intrusion, why it is a problem and what to expect if it is suspected near a home or business.
- Why Test for Vapor Intrusion? (RR-953) or ¿Por Qué Probar la Intrusión de Vapor? (RR-953a: Spanish version) [PDF] - This fact sheet provides information for home and business owners to consider when deciding whether to allow access for vapor intrusion sampling.
- What to Expect During Vapor Intrusion Sampling (RR-954) - This fact sheet helps home and business owners understand the process of collecting sub-slab vapor samples.
- Understanding Chemical Vapor Intrusion Testing Results (RR-977) - This fact sheet helps home and business owners understand laboratory results and explains screening levels.
- Mitigation: Protection from Vapor Intrusion (RR-094) or Mitigación: Protección Contra La Intrusión De Vapor (RR-094a: Spanish version) [PDF] - When test results show contaminant vapors are present in the air below a building, these vapors can get into the indoor air and present a health risk. Options are available to prevent these contaminant vapors from getting indoors, called vapor mitigation. This document explains the basics of mitigation and clarifies roles and responsibilities for maintenance.
- Who Should I Contact About Vapor Intrusion Investigations? (RR-934) - This document defines the responsibilities of the Department of Health Services/Division of Public Health (DHS/DPH), local health departments and DNR staff in assessing and mitigating human health risk at vapor intrusion sites.
- Environmental Contamination & Your Real Estate (RR-973) - When soil or groundwater contamination is discovered in a rural or urban area, one of the questions that homeowners may raise is whether such information will impact the market value of their property and if so, to what extent. This publication discusses the issue.
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.
Vapor Intrusion 101 or Intrusión de Vapor 101 (Spanish version) [exit DNR] - This video, using a hand-drawn/animation technique, introduces the concept of vapor intrusion to people who may be unfamiliar with it by showing the root cause, how it spreads underground, and what can be done about it.
- The Responsible Neighbor, A Vapor Intrusion Story This video for consultants and responsible parties shows how good communication with neighbors benefits everyone involved with an environmental cleanup.
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.
- Vapor Intrusion Outreach Toolkit and Sub-slab Vapor Sampling Procedures Guidance - Terry Evanson and Outreach Staff (DNR)
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
- CLU-IN Focus Website for Vapor Intrusion provides links to technical publications on sampling and analysis and mitigation for vapor intrusion.
Workshops and Conferences
- Indoor Air Vapor Intrusion Database Workshops and Conferences provides access to presentations from past U.S. EPA-sponsored workshops and conferences focused on innovative and evolving ways to address vapor intrusion.
Department of Defense Environmental Security Technology Certification Program (ESTCP)
- Sewers and Utility Tunnels as Preferential Pathways for Volatile Organic Compound Migration into Buildings: Risk Factors and Investigation Protocol provides results from a study on the migration of vapors from a source area within sewers and utilities directly into homes and businesses, identifying a preferential pathway that needs to be considered in the conceptual site model. The final work products include an executive summary, conceptual model and investigation protocol posted December 2018 and a final report posted in January 2019. A two-minute YouTube video on how to collect a vapor sample from within a sewer is included on the website.
Naval Facilities Engineering Command (NAVFAC)
American National Standards Institute (ANSI) / American Association of Radon Scientists and Technologists (AARST)
- ANSI-AARST Standards or ANSI Webstore provide design standards for vapor mitigation that are available for purchase, including SGM-SF-2017, Soil Gas Mitigation Standards for Existing Homes and CC-1000-2017, Soil Gas Control Systems in New Construction of Buildings.
- Vapor Intrusion Mitigation in Existing Buildings
- Passive Sampling for Vapor Intrusion Assessment
- DOD Vapor Intrusion Handbook
American Petroleum Institute
- Collecting and Interpreting Soil Gas Samples from the Vadose Zone: A Practical Strategy for Assessing the Subsurface Vapor-to-Indoor Air Migration Pathway at Petroleum Hydrocarbon Sites
Electric Power Research Institute (EPRI)
Interstate Technology & Regulatory Council (ITRC)
- Petroleum Vapor Intrusion: Fundamentals of Screening, Investigation and Management webinar - This webinar discusses the petroleum vapor intrusion guidance document prepared by ITRC. (1/13/13)
Strategic Environmental Research and Development Program (SERDP) and Environmental Security Technology Certification Program (ESTCP)
- Field Methods to Distinguish Between Vapor Intrusion and Indoor Sources of VOCs - Module 1 - This 30-minute webinar discusses the many consumer products that contribute VOCs to indoor air and how indoor air contaminants can influence sub-slab vapor concentrations.
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|
|South Central||Jeff Ackerman|
|West Central||Candace Sykora|