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Indiana Department of Environmental Management

IDEM > Your Environment > Vapor Intrusion > Vapor Intrusion: FAQs Vapor Intrusion: FAQs

1. What is vapor intrusion?

Vapor intrusion is a term used to describe the process in which chemical vapors from contaminated soil or groundwater affect the indoor air quality in a building. Whenever chemicals are spilled on the ground or leak from an underground storage tank, they can soak into the soil or dissolve into the groundwater and begin to spread. The contaminated soil or groundwater can emit vapors that spread to areas occupied by buildings. Vapors can enter the buildings through cracks in basements, foundations, sewer lines, and any other type of opening. Occasionally, the vapors can increase to concentrations that may be harmful to human health.


2. What chemicals are associated with vapor intrusion?

A class of chemicals known as "volatile organic compounds" (VOCs) is the most common cause of vapor intrusion. Several components of gasoline are included within this classification. Gasoline VOCs include benzene, toluene, ethylbenzene, and xylene (known together as BTEX). Other common sources of vapor intrusion are chlorinated compounds. These are used in dry cleaning and industrial operations. These chemicals include PCE (also known by its chemical name tetrachloroethene) and TCE (also known by its chemical name trichloroethene). Both PCE and TCE can breakdown into other chemicals which can also cause vapor intrusion problems.


3. How could vapor intrusion affect my health?

There are many factors that will determine how one's health could be affected by vapor intrusion. Generally, exposure to high levels of chemical vapors can cause symptoms such as dizziness, respiratory irritation, a burning sensation in the eyes, a headache, and nausea. These symptoms are usually temporary and disappear shortly after the exposure has ended. It is possible for long term exposure (exposure to low levels of chemical vapors over the course of many years) to elevate the risk of cancer or chronic diseases.


4. Where are vapor intrusion issues most likely to occur?

Vapor intrusion is possible at any building where contamination is present in nearby soil or groundwater. It can occur in homes, businesses, churches, government buildings, or any other building. In most cases, vapor intrusion will not be a problem if the soil or groundwater contamination is more than 100 feet away.


5. How is vapor intrusion investigated?

Often, the interpretation of indoor air sampling results is complicated by volatile organic compounds that are normally present within the home or building. These volatile compounds can come from household products. Sometimes hobbies or other activities within the home or building also create indoor air problems.

Since a variety of VOC sources are present in most homes and buildings, testing inside the home or building will not necessarily confirm that VOCs in the indoor air are from nearby VOC contamination. In most cases, the potential for vapor intrusion can be verified or ruled out by collecting soil gas samples or ground water samples near the contamination site. In some cases, it is necessary to sample immediately beneath the home or building or in the living space.


6. Who do I contact if I have vapor intrusion concerns?

Usually vapor intrusion concerns are identified during the investigation of contamination of neighboring sites. If strong petroleum or other chemical odors are noticeable inside a home, it may be advisable to leave the home or call the local fire department. You can contact OLQ vapor intrusion staff or email IDEMRISC at for more information.


7. How do I know if vapor intrusion is a problem at my home or business?

Vapor intrusion is not a common occurrence. It is generally only found when contaminated property is nearby.


8. How do I correct vapor intrusion problems?

The most common solution to vapor intrusion problems is the installation of a vapor intrusion mitigation system. These systems are similar to radon remediation systems, and vent contaminants from the soil below the foundation or basement outside before they can enter the building. A vapor intrusion mitigation system is very simple and uses minimal electricity. Please see the definition of a vapor intrusion mitigation system for more details.


9. I don't have a basement in my home. Do I need to worry about vapor intrusion?

While vapor intrusion is often associated with homes or buildings having basements, all buildings near contaminated sites have the potential to be impacted by vapor intrusion. Any home or building that is located within 100 feet of contamination has the potential for vapor intrusion problems.


For More Information

If you have other questions about vapor intrusion or are concerned about vapor intrusion in your home or a building, you may contact OLQ vapor intrusion staff or email IDEMRISC at