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EPA's Vapor Intrusion Guide
October 2015
This fact sheet provides basic information about
the OSWER Technical Guide for Assessing and
Mitigating the Vapor Intrusion Pathway from
Subsurface Vapor Sources to Indoor Air
[OSWER Publication 9200.2-154, June 2015]
("the Guide"), which may be useful for EPA
staff, state and tribal agencies, local
governments and community organizations,
environmental professionals, and persons
without specific environmental knowledge and
expertise.
What is vapor intrusion?
Vapor intrusion refers to the migration of
chemical vapors from any underground source
into structures (e.g., homes, businesses, schools).
Vapor Intrusion into Indoor Air
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Soil Contamination
Groundwater Contamination
Where and when is vapor intrusion a
potential concern?
Vapor intrusion is a potential concern wherever
buildings or other enclosed structures are located
near an underground source of vapor-forming
contamination. A wide variety of chemical
contaminants can give off vapors, which can
migrate towards and enter buildings or other
enclosed structures as a component of a gas.
Chemical contamination in the ground can arise
from spills and releases above the ground
surface, in addition to releases directly into the
subsurface.
Why is vapor intrusion a potential
concern?
Vapor intrusion is one of many potential ways
that people may come into contact with
hazardous vapors while performing their day-to-
day indoor activities. Depending upon building-
and site-specific circumstances, concentrations
of chemical vapors arising in structures from
vapor intrusion may threaten human health or
safety. When human health or safety is
threatened by vapor intrusion, response action is
warranted.
Why did EPA publish this Guide for
vapor intrusion assessment and
mitigation?
EPA has statutory authority and responsibility to
assess and, if warranted, mitigate vapor intrusion
at hundreds of sites with subsurface
contamination by vapor-forming chemicals. The
Guide was published to promote national
consistency and enhanced approaches in how the
vapor intrusion pathway is addressed at
contaminated sites within EPA's jurisdiction.
How does EPA have authority to
address vapor intrusion?
The sources of EPA authority and requirements
for addressing subsurface vapor intrusion are the
relevant federal statutes and regulations, which
include the Comprehensive Environmental
Response, Compensation, and Liability Act
(Superfund law) as amended ("CERCLA") and
the corrective action provisions of the Resource
Conservation and Recovery Act as amended
("RCRA").
Where and when is EPA's vapor
intrusion Guide to be used? Does it
pertain only to contamination by
chlorinated solvents?

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EPA's Vapor Intrusion Guide
October 2015
This Guide is intended for use at sites within
EPA's jurisdiction that are being evaluated
pursuant to CERCLA or RCRA corrective
action, sites subject to EPA's brownfield grants,
and certain federally operated facilities, where
vapor intrusion may be of potential concern. The
Guide pertains to all of the various vapor-
forming chemicals that may occur as subsurface
contaminants at these sites, which include many
non-chlorinated compounds (petroleum
hydrocarbons, for example) and compounds that
are not used as solvents.
How does EPA's Guide differ from
our 2002 draft guidance?
This Guide reflects recent scientific
developments and additional EPA experience
since our draft guidance was released in 2002,
which have led to enhanced approaches for
evaluating and managing vapor intrusion. These
enhanced approaches include allowing more
flexibility in the sequencing of subsurface and
interior/indoor sample collection, allowing more
flexibility in sampling durations and methods to
take advantage of technical developments,
describing specific methodologies for evaluating
indoor air contamination arising from sources
other than vapor intrusion, and using multiple
lines of evidence in evaluating and making
decisions about vapor intrusion. The Guide also
describes response actions (including building
mitigation options) for addressing vapor
intrusion, and discusses when institutional
controls are appropriate to address the vapor
intrusion pathway.
How does EPA's Guide work with
guidance prepared by other entities?
EPA's Guide reflects the current state of the
science and is appropriate for its intended scope
and purpose. EPA recommends that state
agencies that have delegated authority to
implement CERCLA or RCRA consider the
Guide when implementing their state-specific
guidance for vapor intrusion assessment and
mitigation, if any. EPA anticipates that some
states, tribes, and local governments will find the
Guide useful for their respective cleanup and
land revitalization programs also.
How does EPA's Guide work with
standards for real estate
transactions?
EPA's Guide does not aim or intend to offer
recommendations for vapor intrusion
assessments that private parties choose to
conduct as part of real estate transactions. Nor
does this Guide modify existing EPA guidance
regarding landowner liability protection (e.g.,
All Appropriate Inquiries, the bona fide
prospective purchaser provision). On the other
hand, EPA anticipates that private parties and
environmental professionals will find EPA's
Guide useful for understanding EPA's
recommendations and expectations for
assessment and cleanup.
On-line Resources
To obtain the Guide, please visit EPA's web site
at:
https ://www.epa. gov/vaporintrusion/technical-
guide-assessing-and-mitigating-vapor-intrusion-
pathwav-subsurface-vapor
Additional information about EPA's cleanup and
land revitalization programs and our authorizing
statutes is available at:
http://www2.epa.gov/aboutepa/about-office-
solid-waste-and-emergencv-response-oswer
Additional information about assessing the
likelihood of contamination on a property is
available at:
https://www.epa.gov/brownfields/brownfields-
all-appropriate-inquiries

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