Vapor Intrusion

What is vapor intrusion?

Vapor intrusion happens when chemicals under the ground seep into the air in your home. Chemicals can be released into the soil or groundwater if there is a chemical spill on the ground, or from a leak in an underground petroleum storage tank. Vapor intrusion can make the air inside your home unsafe.

There could be a greater chance of vapor intrusion if you live near an old industrial site, dry cleaners, or gas stations.

What chemicals might enter a home or building as a result of vapor intrusion?

Vapor intrusion usually happens when volatile organic compounds (VOCs) migrate from the ground into a building. These VOCs can include benzene, toluene, ethylbenzene, trichloroethylene (TCE), and tetrachloroethylene (PEC).

What health effects can occur from vapor intrusion?

The health effects can be different for each person. The effects can also change depending on the chemicals involved. When people are exposed to high levels of chemicals indoors (high enough that it smells), they might have itchy eyes, trouble breathing, headaches, and nausea. Symptoms usually get better when individuals are no longer exposed. Exposure to some of these chemicals over a long period of time may increase a person’s lifetime risk of developing cancer. Children, older adults, and people who have breathing problems, like asthma, are more likely to have health problems from vapor intrusion.

How can I reduce the potential for vapor intrusion?

One way to reduce vapor intrusion is to install a vapor intrusion mitigation system. The two most common types of systems of systems are sub-slab and sub-membrane depressurization systems. Both systems must be powered on all the time to be effective. These systems reduce the possibility for soil gases to travel indoors, allow vapors to be vented to the outside, and use minimal electricity. A professional should check the systems regularly to make sure they’re working. Another solution is to seal cracks in foundations to decrease the possibility for vapors to travel indoors.

How can I improve air quality inside my home?

One of the primary causes of indoor air quality problems in the home is VOC migration. VOCs found in household products (paint, cleaning supplies, moth balls, air fresheners, hobby supplies) are more likely to be a source of indoor air quality problems than vapor intrusion from a chemical spill. VOC levels tend to be ten times higher indoors than outdoors.

To improve air quality, you can take the following steps:

  • Use unscented, non-hazardous household cleaning products such as vinegar and baking soda.
  • Maintain proper air circulation and humidity levels in the home, especially when using household products.
  • Use HEPA filters, dehumidifiers, and exhaust fans to improve air quality. Bathroom exhaust fans should exhaust above the roofline, and kitchen oven hood fans should exhaust to the outside.
  • Ensure that heating systems, appliances (wood burning ovens, kerosene heaters), and fireplaces are properly vented and in good condition. Perform annual checks as needed.
  • Remove potential health hazards in the home such as lead, mold, radon, pesticides, and other contaminants. Removal may require a skilled professional.
  • Install a carbon monoxide monitor or alarm in the home. Carbon monoxide monitors are available at home improvement stores.
  • Change or clean filters regularly to remove air pollutants.
  • Do not smoke or vape indoors.

Should I test my indoor air if I suspect vapor intrusion?

If you believe your home has been affected by vapor intrusion, contact an indoor air quality professional. Before hiring a professional, consider their certifications and memberships. VDH does not keep a listing of indoor air professionals, and cannot recommend specific environmental companies.

Where can I get more information about vapor intrusion?

This fact sheet was made possible by a cooperative agreement [program # CDC-RFA-TS-23-0001] from the Agency for Toxic Substances and Disease Registry (ATSDR). Its contents are solely the responsibility of the Virginia Department of Health, toxicology program and do not necessarily represent the official views of the ATSDR, or the U.S. Department of Health and Human Services.

Last Updated: July 15, 2025