Engineering and Expeditionary Warfare Center

Vapor Intrusion




Vapor intrusion (VI) is the migration of volatile chemicals from the subsurface into indoor air. It is important to take VI processes into consideration where soil or groundwater is contaminated with volatile compounds and current or future land use scenarios suggest a potential human exposure pathway to indoor air.

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Prior to initiating a VI evaluation associated with a Department of the Navy (DON) environmental release, it is important to confirm that chemicals in subsurface media are of sufficient volatility and toxicity to pose a potential VI concern and there is a potential complete human exposure pathway to indoor air. Assessing the VI pathway can be conducted at any point in the Environmental Restoration (ER) process (e.g., investigations, remediation, five-year reviews, etc.). The VI potential in existing buildings should be evaluated based on multiple lines of evidence (e.g., air, soil gas, distance to building, indoor sources, and building characteristics). Future VI potential should be assessed based on those lines of evidence that are applicable to reasonably anticipated future use.

At Environmental Restoration Program (ERP) sites where VI is occurring and posing an unacceptable risk to human health, the Remedial Project Manager (RPM) should make appropriate risk management decisions to mitigate the VI risk. Even if there is no current unacceptable VI risk, risk management decisions to address potential future VI risk may need to be further considered when a subsurface vapor source remains at a site.

The Department of Defense (DoD) Vapor Intrusion Handbook currently serves as DON’s guidance on VI. To ensure relevancy is maintained, handbook updates are issued as needed through a series of fact sheets prepared by the Tri-Service Environmental Risk Assessment Workgroup (TSERAWG). The TSERWG VI fact sheets can be accessed here. The Handbook uses a three-tiered approach to assess human health risks related to the VI pathway as follows: 

  • Tier 1 Screening Level Evaluation: To identify sites that warrant further VI consideration or determine VI is not a pathway of concern.
  • Tier 2 Site-Specific Evaluation: To weigh multiple lines of evidence and refine the conceptual site model (CSM) for conclusions of VI occurrence (current VI in buildings) or potential to occur.
  • Tier 3 Risk Management and Mitigation: If VI is occurring and posing an unacceptable risk, the RPM should make appropriate risk management decisions to mitigate the VI risk. In DON non-residential buildings, the RPM should collaborate and coordinate with DON Occupational Safety and Health professionals to identify unacceptable risk/exposures and potential exposure mitigation measures. 


RPMs should also be aware of site-specific requirements as many states have developed or are in the process of developing their own VI guidance. It is important to keep in mind that not all state health agencies follow a tiered approach. RPMs should coordinate with their regulators to identify the technical approach that is most appropriate for their site. For more information, Chapter 13.6 of the DON Environmental Restoration Program Manual details VI management considerations.





Title and Description

ERP Manual

DON Environmental Restoration Program Manual: Chapter 13.6 Vapor Intrusion (February 2018)

Defines VI and describes the guidance and policies available to RPMs to evaluate the VI pathway based upon multiple lines of evidence.

Petroleum VI

Technical Guide for Addressing Petroleum Vapor Intrusion at Leaking Underground Storage Tank Sites (2019)

This EPA guidance specifically focuses on VI from petroleum sources. It provides screening criteria based on physical separation distances between vapor sources and potential receptors based on data specific to leaking underground storage tank (UST) sources.


Indoor Air

OSWER Technical Guide for Assessing and Mitigating the Vapor Intrusion Pathway from Subsurface Vapor Sources to Indoor Air (June 2015)

 This technical guide presents current technical recommendations of the EPA based on the current understanding of vapor intrusion into indoor air from subsurface vapor sources. One of its main purposes is to promote consistency in assessing the vapor intrusion pathway. It provides a flexible science-based approach to assessment that accommodates the different circumstances (e.g., stage of the cleanup process) in which vapor intrusion is first considered at a site and differences among pertinent EPA programs

Risk Communication

NAVFAC/NMCPHC Guidance for Communicating Vapor Intrusion at Environmental Restoration Sites (October 2014)

Provides RPMs with recommendations for notifying and relaying information regarding VI investigations to Base personnel and potentially affected occupants of industrial, office, or residential buildings.

Background Chemicals

NAVFAC Interim Final Guidance for Environmental Background Analysis Volume IV: Vapor Intrusion Pathway (April 2011)

Reviews methodologies for assessing potential background sources to indoor air as a part of the assessment of the VI pathway.

DoD VI Handbook

DoD Vapor Intrusion Handbook (January 2009)

Outlines the process for the evaluation and investigation of the VI pathway at DoD sites.

VI Policy

Navy/Marine Corps Policy on Vapor Intrusion (April 2008)

Provides direction on the evaluation and remediation of the VI pathway. Topics covered include determining whether to evaluate the VI pathway for a site, planning and implementing a VI pathway evaluation, addressing background chemical issues, evaluating risk for human health exposures, evaluating remedial alternatives, and considering previously transferred property.

Background Chemicals

Navy Policy on the Use of Background Chemical Levels (January 2004)

Defines the DON position on consideration of background chemicals as applied to the DON ERP and clarifies the interpretation of EPA’s “Role of Background in the CERCLA Cleanup Program.”


Title and Description

Continuous Monitoring for Vapor Intrusion

Continuous Monitoring for Vapor Intrusion Fact Sheet (2021)

This fact sheet discusses the assessment of vapor intrusion (VI) which are complicated by a high degree of spatial and temporal variability. This fact sheet will focus on recent applications of a continuous monitoring (CM) technology that provides quantitative measurements of vapor concentrations in the field. CM can help to address site-specific building conditions that influence the VI pathway over time.

Preferential Pathways

DoD Vapor Intrusion Handbook Fact Sheet Update – Vapor Intrusion Preferential Pathways (VIPPs) (September 2020)

Includes an updated conceptual model with scenarios for sites with higher and lower risk for VIPPs and new methods for sampling preferential pathways.


DoD Vapor Intrusion Handbook Fact Sheet Update – Considering the Vapor Intrusion Pathway throughout the CERCLA Process (May 2020)

Provides a roadmap for assessing the VI pathway at DoD facilities under CERCLA.



DoD Vapor Intrusion Handbook Fact Sheet Update – Matrix for Selecting Vapor Intrusion Investigation Technologies (July 2019)

Provides a matrix that facilitates the selection of the most effective technologies for investigating the Vapor Intrusion pathway at DoD facilities.

Background Chemicals

DoD Vapor Intrusion Handbook Fact Sheet Update - Determining the Influence of Background Sources on Indoor Air Concentrations in Vapor Intrusion Assessment (September 2017)

Describes field and calculation methods for determining the influence of background sources and for developing background investigation strategies.

Tracers, Surrogates, Indicator Parameters

DoD Vapor Intrusion Handbook Fact Sheet Update -  Use of Tracers, Surrogates, and Indicator Parameters in Vapor Intrusion Assessment (September 2017)

Describes how tracers, surrogates, and indicator parameters can be used to guide VI and background investigations.

Building Pressure Cycling

DoD Vapor Intrusion Handbook Fact Sheet Update -  Use of Building Pressure Cycling for Vapor Intrusion Assessment (August 2017)

Describes an investigation technique to control building air pressure and ventilation to promote VI in order to assist in determining its influence on indoor air quality compared to background factors.

High Volume Soil Gas Sampling

DoD Vapor Intrusion Handbook Fact Sheet Update – High Volume Soil Gas Sampling for Vapor Intrusion Assessment (February 2017)

Provides a high-level summary of high volume sampling (HVS), which is a method for assessing vapor concentrations and distributions in the subsurface and is well suited to sub-slab soil vapor sampling as part of a VI assessment.

Passive Sampling

DoD Vapor Intrusion Handbook Fact Sheet Update - Passive Sampling for Vapor Intrusion Assessment (February 2017)

Provides a high-level summary of the application and interpretation of passive sampler data for vapor intrusion assessments.

Real-Time Monitoring

DoD Vapor Intrusion Handbook Fact Sheet Update - Real-Time Monitoring for Vapor Intrusion Assessment (February 2017)

Provides a high-level summary of the collection of real-time monitoring data related to indoor air and soil vapor concentrations, building pressure differentials and ventilation rates, and tracer gas concentrations.

Passive Sampling

Passive Sampling for Vapor Intrusion Assessment (July 2015)

Describes the basics of passive sampler theory and design, the available types of passive samplers, the advantages and limitations of passive samplers, and important considerations when implementing a passive sampling program. In addition, the results from two VI case studies are highlighted.

Site Characterization

Innovative Vapor Intrusion Site Characterization Methods Fact Sheet (February 2013)

Provides an overview of several emerging and innovative methods for the characterization of indoor air at potential VI sites. These methods include passive sampling, use of a portable gas chromatography/mass spectrometry (GC/MS) instrument, use of building pressure control techniques, hydrocarbon fingerprinting, compound specific isotope analysis (CSIA), and radon sampling.


New Buildings

Vapor Intrusion Mitigation in Construction of New Buildings (August 2011)

Provides an overview of VI mitigation methods that can be integrated during the construction of new buildings, along with important factors to consider when selecting and designing these systems.


Existing Buildings

Vapor Intrusion Mitigation in Existing Building (May 2011)

Reviews methods that can be used to mitigate VI in existing buildings, along with important considerations for selecting and designing an appropriate mitigation system.

VI Research

Real-Time Monitors

Navy Environmental Sustainability Development to Integration (NESDI) 568: Evaluation of Various Real-Time Monitors to Accelerate On-Site Analysis for Vapor Intrusion (2019)

Demonstrates reliable on-site mobile analyzers for indoor air and soil gas samples that can be used to expedite VI investigations.

Carbon Filters

NESDI 571: Innovative Activated Carbon Filters to Address Vapor Intrusion within Commercial/Industrial Buildings (2019)

Demonstrates air filtration systems for effectiveness in the removal of trichloroethylene from indoor air.

Temporal Variability

NESDI 554: Temporal Variability Vapor Intrusion Assessments (June 2018)

Updates the previous VI decision framework by addressing data gaps regarding temporal and spatial variability of VI data.

Industrial Building

Attenuation Factors 

NESDI 476: A Quantitative Decision Framework for Assessing Navy Vapor Intrusion Sites - Fact Sheet (April 2016)

Reviews the DON VI assessment framework used to evaluate and interpret VI data and building characteristics. It can be used to prioritize buildings for further assessment, assess the likelihood of VI occurrence in individual buildings, and plan for the long-term stewardship of current and future buildings.

Quantitative Decision Framework

NESDI 476: A Quantitative Decision Framework for Assessing Navy Vapor Intrusion Sites (June 2015)

Describes a quantitative decision framework to improve decision-making and site management practices for DON industrial/commercial VI sites.

VI Research Data Gaps

Review of Best Practices, Knowledge and Data Gaps, and Research Opportunities for the U.S. Department of Navy Vapor Intrusion Focus Areas, SPAWAR Systems Center Pacific (May 2009)

Reviews best practices, the state-of-knowledge and data gaps, and provides a summary of research directions for VI related to passive sampling, background sources, and improved subsurface sampling techniques.


Title and Description


NAVFAC Investigating Vapor Intrusion: Portable GC/MS Video (June 2013)

Provides a quick overview of how to use a portable gas chromatograph mass spectrometer (GC/MS) technology and shows the value of real-time data collection for vapor intrusion sites.

EPA Tool

EPA Spreadsheet for Modeling Subsurface Vapor Intrusion

This spreadsheet tool based on the analytical solutions of Johnson and Ettinger allows the user to estimate indoor air concentrations from subsurface vapor intrusion into buildings. *Not Applicable for use in all states*

EPA Database

EPA Vapor Intrusion Database

EPA’s VI Database contains data to support site-specific estimates of vapor attenuation factors. This database is applicable primarily to use for residential buildings.

EPA Calculator

EPA Vapor Intrusion Screening Level (VISL) Calculator

The calculator provides media-specific, risk-based screening-level concentrations for:  groundwater, near-source soil gas, sub-slab soil gas, and indoor air.

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