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VET performs vapor intrusion evaluations at residential, commercial, and industrial properties. These investigations help to determine if migration of volatile organic compounds (VOCs) into buildings from contaminated soil or groundwater has contributed to indoor air quality concerns. Vapor intrusion of VOCs, semi-volatile organic compounds (SVOCs), elemental mercury, and pesticides, for example, can accumulate in indoor air and cause immediate or long-term health effects to building occupants. Conducting a vapor intrusion evaluation and taking the necessary steps to resolve vapor intrusion issues at your property helps you protect your investment, from the health of your employees or family to the long-term value of your property.

Vapor intrusion refers to the intrusion of chemicals from contaminated soil or groundwater into a building. It becomes an issue when soil or groundwater beneath a building is contaminated with volatile chemicals or petroleum products. These substances release vapors that can enter buildings and accumulate in indoor air. Contaminants from petroleum spills, dry-cleaning, and pesticide application, can cause vapor intrusion.
Due to their volatile nature, VOCs present in soil or groundwater have the potential to migrate into structures through utility pathways or cracks in building foundations. Vapor intrusion is a concern for properties with existing structures and for properties where structures may be developed in the future. Exposure to VOCs in indoor air can damage the central nervous system, liver, and kidneys. Some chemicals may cause eye irritation, headaches, or nausea. Long-term exposure to chemical vapors in indoor air can cause more serious chronic diseases, with some believed to cause cancer in humans.
The amount of contamination, the properties of subsurface soil, building construction, ventilation, and many other factors affect the likelihood and severity of vapor intrusion. The only way to understand the nature and extent of vapor intrusion is to sample the indoor air of a structure. VET performs vapor intrusion evaluations that target your specific property. Our vapor intrusion evaluations are tailored to the potential source of contamination and the condition of the building being evaluated. Our targeted and detailed evaluations provide the information you need to help you make well-informed decisions for your property.
Click here for additional information on vapor intrusion provided by the United States Environmental Protection Agency.

VOCs are organic chemicals that release vapors under normal indoor atmospheric conditions. The volatility of a chemical is determined by its boiling point, which corresponds to how easily the chemical will be emitted. Very volatile organic compounds have a boiling point between <0 to 50-100°C (propane, butane, methyl chloride). Other less volatile compounds have a boiling point between 240-260 to 380-400°C (pesticides such as DDT, fire retardants, and polychlorinated biphenyls (PCBs)).

VOCs may be present in soil or groundwater due to historic spills or mishandling of hazardous materials. Vapors released from VOCs in soil and groundwater can travel through the air spaces between soil particles (soil gas). These vapors naturally migrate upward. The rate of migration depends on the composition of the soil and pressure changes from climatic conditions, utility pathways, and pressure differentials created by heating ventilation and air conditioning (HVAC) systems in buildings.
For a technical overview of volatile compounds provided by the United States Environmental Protection Agency, click here.

Depending on where you live, where you work, the history of your property, and the condition of your buildings, vapor intrusion has the potential to affect everyone. When in doubt, call VET to gain an understanding of your potential exposure to vapor intrusion.
Homeowners
If there has been a spill of a hazardous substance or petroleum substance reaching soil or groundwater on or near your property, your home may be impacted by vapor intrusion. If you live near commercial or industrial facilities that currently or historically handled or manufactured hazardous chemicals or petroleum products, including dry cleaning facilities, photo or print shops, or gas stations, vapor intrusion may be a concern for your home. The proximity of your home to federal or state cleanup sites may also impact your vulnerability to vapor intrusion concerns.
Business Owners
Many businesses handle materials that contain VOCs. Historically, proper handling and disposing of potentially hazardous materials was not well understood, practiced, nor regulated. Even if your facility conducts all operations by the book, it’s possible that previous occupants of your building(s) may not have done the same. A historic spill or improper handling and disposal of VOCs has the potential to cause vapor intrusion at your facility. The proximity of your facility to federal or state cleanup sites may also impact your vulnerability to vapor intrusion concerns.

Commercial and Industrial Workers
If you work at or near a commercial or industrial facility where hazardous chemicals or petroleum substances were handled historically or are handled currently, you may be concerned about vapor intrusion. Your employer may have established engineering controls, work practices, or personal protective equipment to address a variety of environmental concerns. If you are concerned about potential or reported releases of VOCs, ask your employer about your workplace-specific safety measures that address vapor intrusion.
Developers and Prospective Buyers
Prior to investing in developing a property for residential, commercial, or industrial use, developers should be aware of all potential environmental concerns at a property. Conducting a Phase I Environmental Site Assessment (ESA) prior to purchase and development of a property will identify potential sources of vapor intrusion on or near the property. VET will perform and in-depth Phase I ESA and recommend additional investigation, if warranted by the identification of vapor intrusion concerns.

The following are indicators that vapor intrusion may be a concern at your property:
- A Phase I Environmental Site Assessment identified a vapor encroachment concern (VEC) on or near the property (See VET’s Phase I page for more information about VECs.)
- Environmental investigations, such as a Phase II Environmental Site Assessment, identified VOC soil or groundwater contamination on or near the property.
- Workers or occupants complain of health effects that warrant evaluation of indoor air.
- A documented or reported spill of a hazardous substance or petroleum product has occurred on or near the property.

Being aware of potential indoor air problems and seeking professional guidance is the first step! If current operations or historical uses of your property indicate that vapor intrusion could be an issue, VET will conduct a vapor intrusion evaluation. To assess whether vapor intrusion is affecting your building, VET will investigate the history of the site and conduct indoor air and/or soil gas sampling for analysis of the suspected chemicals of concern. USEPA and states have developed screening levels for indoor air exposure.
A paired indoor air and soil gas sampling event can help determine if indoor air contamination is attributable to intrusion of subsurface contamination or if the condition is the result of current facility operations. VET will compare results from your vapor intrusion evaluation to regulatory screening levels to determine if levels of VOCs are acceptable. For more information about screening levels for specific contaminants, click here.
VET’s vapor intrusion evaluations are accompanied by a comprehensive indoor air survey that may identify additional sources of indoor air contamination at your property. Vapor intrusion evaluations may be conducted for peace of mind or may be mandated by a regulatory agency. Resolving indoor air problems can improve your workers’ or family’s health. When you work with VET to evaluate vapor intrusion concerns, we do what makes sense for you.

Vapor intrusion may be resolved by removing the source of contamination in soil or groundwater. If removal of the source contamination is not possible, then a vapor mitigation system may be installed. One type of vapor mitigation system is an active sub-slab depressurization system (SSDS). An SSDS typically consists of a fan that draws air from the soil beneath a building and discharges it to the atmosphere through a piping system, effectively causing the chemical(s) of concern to bypass the building.
Post-mitigation or post-remediation sampling is crucial to make sure the mitigation system or remediation project effectively reduced or eliminated the vapor intrusion issue. VET installs vapor mitigation systems and conducts post-mitigation monitoring to ensure concentrations of harmful vapors are below applicable regulatory screening levels.
Click here for documentation from the United States Environmental Protection Agency regarding vapor intrusion mitigation approaches.

Vapor intrusion of VOCs from beneath a building is not the only source of indoor air contamination. VOCs are found in paints, air fresheners, scented candles, stored fuels, cleaning materials, cologne and perfume, building materials, and many other products, including common hobby supplies. VOCs from these commonly used sources in residential, commercial, and industrial facilities have the potential to accumulate in indoor air. Non-VOC indoor air concerns include radon, asbestos, lead, and mold, among many other site-specific contaminants.
VET performs area and personal air monitoring for a wide range of indoor air contaminants based on workplace conditions or other specific health concerns in residential or workplace settings. You may wish to include an additional indoor air investigation with a vapor intrusion evaluation. For example, radon entry into buildings occurs in a similar fashion to vapor intrusion, therefore coupling radon measurement and a vapor intrusion evaluation can be time and cost-effective and ensure you have a full understanding of the indoor air concerns at your property. VET will tailor a vapor intrusion evaluation and any necessary additional indoor air investigations to meet your needs and budget!