Vapor intrusion. You’ve heard about it on the news, but you still aren’t exactly sure what it is, why it happens, or how it could potentially impact your health. CTEH experts are here to explain more:

What is vapor intrusion?
Vapor intrusion occurs when volatile organic chemicals such as those found in petroleum products like gasoline or diesel fuel; cleaning solvents; or industrial degreasers are present in the ground underneath or near an enclosed structure. This often occurs when these substances are spilled on the ground and/or leak from underground sources. These substances can give off vapors that move up through soil and then enter into buildings through openings such as sewer lines or cracks in foundations or slabs.

What is the likelihood that health issues may arise from vapor intrusion?
Whether or not health effects arise from vapor intrusion into occupied living or working spaces is highly dependent on the type of chemical and what levels people breathe. These factors, as well as the duration of exposure and current health status, all determine the likelihood that adverse health effects will occur.

How do scientists determine if vapor intrusion is happening?
Vapor intrusion can be challenging to pinpoint due to the sheer number of common household chemicals stored within businesses and homes. These “background sources” can make it hard to tell if vapors are coming from an underground source, an indoor source and/or a neighboring source such as a gas station or industrial facility. For example, when individuals store a gasoline-powered mower and gasoline container in the garage or shed, this can contribute a significant “background” source of petroleum hydrocarbons to indoor air, which is difficult to distinguish from a subsurface source or it may mask other sources completely.

If the potential for vapor intrusion exists at a contaminated site, qualified environmental scientists can collect soil and groundwater samples. They can also collect soil gas or vapor samples from the affected property and within the building, including from under the foundation (i.e., sub-slab samples). At CTEH, we prepare and implement site-specific sampling and monitoring plans; identify and reduce background sources; and work hard to find and address issues as quickly and effectively as possible.

How are vapor intrusion issues addressed?
Remedies for vapor intrusion vary depending on the severity of the issue. Sometimes, ventilation systems are installed to remove vapors below basements or foundations before they can enter structures. These vapors are then vented outside and away from indoor spaces. Depending on the structure, floor coverings such as a vapor shields may be installed. Following vapor intrusion sampling, CTEH public health experts always walk our partners through the results so they can better understand next steps, effectively communicate any risks and minimize potential disruptions.

Do you have questions about vapor intrusion investigations or assessments? Contact us at