Vapor intrusion investigations

Vapor intrusion sometimes occurs where chemicals were spilled, leaked, or dumped and not cleaned up. For example, properties such as gas stations, dry cleaners, or businesses operating metal parts degreasers use chemicals like gasoline or solvents that can cause vapor intrusion. If these chemicals are mishandled and get into the ground, they can move through the soil and groundwater.

Although the chemicals are often released as liquid, they easily evaporate, becoming a vapor in the air that you often cannot see or smell. At some point, the vapors may come in contact with your home or business – usually around your basement or your floor. These vapors may get into your home through openings such as cracks, or other openings around pipes and sumps. This is a concern because you may breathe in these harmful vapors without knowing.

Vapor intrusion can cause the air in your home to be unsafe to breathe. These chemicals can harm your health at levels well below what people can see or smell. Depending on the amount and type of chemicals, even a short time of breathing them can cause long-term and serious health problems.

Once you know you have vapor intrusion issues, there are simple things that can be done to keep you and your family safe. For example, a vapor mitigation system may need to be installed. This will keep unsafe levels of chemicals from getting into your home and the air you breathe. Most of the time, these systems are very similar to what is used to prevent radon from getting into homes.

How is vapor intrusion investigated?

Step 1

Volatile chemicals are identified in the soil, groundwater, or vapors coming from the soil

Chemicals used by dry cleaners and businesses that used degreases to clean metal parts may cause vapor intrusion.

These types of chemicals can have harmful vapors and may pose a potential risk if the chemicals are spilled, leaked, or intentionally dumped onto the ground.

Another potential source is gas stations that have had a release of petroleum from their underground storage tanks.

Step 2

Sample for vapors underground to determine the area of concern

Crews will drill into the ground to collect soil, groundwater, and vapor samples.

The sampling area may grow or shrink based upon test results.

Step 3

Test for vapor intrusion inside homes and buildings within the area of concern

Testing from Step 2 determines the area of concern. This is the area where testing shows that vapor intrusion may occur in buildings.

Testing beneath your home for vapors is called sub-slab vapor sampling. It involves drilling small holes in your basement floor or slab to collect vapor samples from under the building. Indoor air samples may be collected as well.

Step 4

Take steps to make buildings safe for people

If testing finds vapor intrusion is a problem, a vapor mitigation system is installed. This system keeps harmful underground vapors from entering the building.

Vapor mitigation systems are simple and reliable when used correctly. They work like a vacuum to keep the vapors from entering the building.

Step 5

Determine the long-term solution

Review chemical release data. WHO? reviews data to determine if cleanup of the chemical release is possible. If so, what is the best way to do it? WHO? works with and shares information with local governments and affected parties.

Solution. Vapor mitigation systems are the short-term solution to manage risks while the long-term feasibility of cleaning up the release is studied, and when possible, implemented.

Follow-up. Some mitigation systems require visits from trained staff to assure they are working as they should be.