Vapor Intrusion

What is vapor intrusion?

Vapor intrusion occurs when chemicals migrate from contaminated groundwater or soil and move into the indoor air through a building’s foundation. Chemicals can be released into the soil or groundwater if there is a chemical spill on the ground, or there is a leak from an underground petroleum storage tank. Vapor intrusion can reduce indoor air quality. 

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

Vapor intrusion generally occurs when volatile organic compounds (VOC) migrate from the ground into a building. These VOCs can include benzene, toluene, ethylbenzene, trichloroethylene (TCE), or tetrachloroethylene (PEC), as well as other VOCs.  

What health effects can occur from vapor intrusion?

Health effects can be different for each person and vary depending on the chemicals involved. When people are exposed to high levels of chemicals indoors (high enough to produce an odor), they may experience symptoms such as eye and respiratory irritation, headache, and nausea. Symptoms usually lessen when individuals are no longer exposed. Exposure to some chemicals over a long period of time may increase a person’s lifetime risk of developing cancer. Individuals who are more prone to health effects include children, the elderly, and those with current respiratory problems such as asthma.  

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 are the sub-slab depressurization systems and the sub-membrane depressurization systems, which must operate continuously 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 periodically check the systems to ensure proper functioning. 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.  

You may be at greater risk for vapor intrusion if you live near an old industrial site, dry cleaner’s, or gas station.  

Where can I get more information about vapor intrusion?


Updated 2023