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Do I Need to Worry About Vapor Intrusion?

An Overview of Vapor Intrusion

In the 1980’s news began to make headlines with concerns about radon gas migrating up through the soil and into basements, homes and other buildings. Since then we have become ever more aware of, and concerned about, soil vapor intrusion; especially from chlorinated solvents and petroleum hydrocarbons. The United States Environmental Protection Agency (EPA) has now identified a list of the types of vapor-forming chemicals including: 

  • Volatile organic compounds (VOCs), such as trichloroethylene and benzene
  • Certain semi-volatile organic compounds, such as naphthalene
  • Elemental mercury
  • Hexavalent chromium
  • Some polychlorinated biphenyls and pesticides

How Does Vapor Intrusion Occur?

Primary sources of these petroleum or chlorine based contaminants in the soil beneath the surface are from spills, illegal dumps, excessive use of chemicals in the past or from pesticide build up. The toxins then migrate from these dump sites through the soil and into groundwater that flows into underground aquifers. From there, the volatile gasses move up through the substrate, creating soil contamination and pooling beneath buildings. The most likely entry of chemical vapors is from leakage through openings in cracked foundations, basements or sewer lines. Depending on what the compounds are, some can even migrate through the floor slab.

Harmful Effects of Vapor Intrusion

Breathing the fumes from chlorinated solvents can be hazardous to human health. Some of them are known carcinogens, while other toxic chemical vapors can affect the central nervous system, or can cause dizziness and fatigue. Even low concentrations of vapor-forming chemicals inside of buildings are an unacceptable health risk, especially after long-term, chronic exposure. In rare and extreme cases, vapor accumulation can even lead to safety hazards, such as explosions, or cause acute health problems.

The good news is, that chemical vapors (VOCs) or soil gasses (like radon) from soil or groundwater contamination near your site can be diverted from beneath your building(s) and safely released into the outdoors. In this way the air quality inside will once again be safe for inhabitants, guests, workers and employees.

Benefits of Soil Vapor Intrusion Testing

Environmental laboratories, environmental consultants and other professionals, work with landowners and building owners to do soil vapor testing and take quality samples of indoor air. These samples are then carefully tested for all suspected contaminants and the results are reported with an extensive review of the results. From this point, the same team will work together to determine what can and should be done to mitigate any negative results.

Vapor intrusion problems in apartment buildings, factories, warehouses or office buildings, can generally be solved by installing a vapor mitigation system. These systems are sub-slab depressurization units that capture and redirect soil vapors from under the foundation of the building before they enter a building and contaminate indoor air. Vapors are vented to the outside of the building where they disperse into the air and are rendered harmless. These systems have been used for years in a safe and effective manner and give everyone greater peace of mind.

After a vapor mitigation system has been installed, follow up soil vapor testing and indoor and outdoor air testing will normally be required for between three to six months. Buildings’ mitigation systems become and are usually considered permanent fixtures of those buildings.


In order to identify soil vapor intrusion in your building, you will need to work closely with an environmental testing laboratory that has the most updated equipment and years of experience with soil vapor testing. It is important too that their customer service is able to carefully explain the results of the testing and work with you and local authorities to mitigate any problems that are revealed.

Torrent Laboratory offers two types of soil vapor intrusion sampling: regular and low-level reporting. The regular TO-15 test method, which has reporting limits of around 0.5 ppbv, is sufficient for most soil vapor monitoring. For residential or commercial environmental screening levels (ESLs), we offer low-level reporting. We use the TO-15 SIM technique, a sensitive methodology that can report data at the 0.005 ppbv level, ideal for the most precise applications. Torrent Laboratory provides the most advanced capabilities and newest technologies, as well as unrivaled customer support.