What Is Vapor Intrusion & Is It Happening on My Property?

Let’s take a look at this insidious threat to your tenants, employees, and business so that you can see the effectiveness of vapor intrusion mitigation measures for improving indoor air quality.

What Is Vapor Intrusion?

Vapor intrusion occurs when vapors from volatile chemical pollutants in the soil or groundwater migrate into nearby structures, posing a threat to the health of the occupants.

Volatile organic compounds (VOCs) that have leaked into the environment can continue to produce harmful vapors for decades. These vapors move through soil and may be able to penetrate your building foundation or concrete slab. They can then become concentrated, especially in basements and subsurface rooms.

Vapor intrusion was initially identified in buildings contaminated by naturally occurring radon gas. Today it’s mostly associated with widely used VOCs and other chemicals including:

• Automotive gas and petrochemicals
• Dry cleaning compounds
• Pesticides

It commonly occurs in residential or commercial buildings close to gas stations, oil wells, and industrial plants or where harmful chemicals have been dumped illegally.

Why Is It Dangerous?

Vapors rising from VOCs are hard to detect and can be harmful at even relatively low levels of concentration. They are also a deceptive threat because people can become used to bad odors or discount symptoms caused by exposure to harmful vapors.

Short-term symptoms from exposure to high levels of vapor pollution include:

• Eye irritation
• Difficulty breathing
• Nausea
• Headache

Long-term exposure to VOCs like benzene and associated chemicals may raise a person’s risk of developing cancer.

As a property owner or manager, you are also potentially liable if a tenant or employee can prove they became ill as a result of exposure to harmful vapors on your property.

Is Vapor Intrusion Happening on My Property?

Most owners or landlords only discover they have a vapor problem when tenants or employees complain of odors or have physical symptoms. Real estate inspections can also reveal vapor intrusion problems. 

If you have a property that’s close to commercial land or where chemicals may have been dumped, you might want to have it tested.

How Is Testing Done?

Trained air quality professionals perform vapor intrusion testing. Three different types of testing are typically used:

• Grab Sampling: A one-time “grab” of air from an area suspected of contamination is analyzed for specific contaminants. This is most often done to check air quality after a spill or accident, or before allowing workers to enter a suspected contaminated area.
• Short-Term Exposure Sampling: Air sampled for 15 to 30 minutes is compared with regulatory exposure limits for many different types of pollutants. Several samples may be taken to see if exposure peaks or fluctuates over time.
• Full-Term Exposure Sampling: Air quality is evaluated over a longer period, such as an eight-hour shift, to determine a time-weighted average for exposure to contaminants of concern.

Short and full-term sampling is most often used when there is a suspicion of vapor intrusion into a residential or commercial building.

Read More: Industrial Hygiene and Indoor Air Quality Assessments

What Can Be Done to Prevent Vapor Intrusion?

Once the intrusion of harmful vapors has been confirmed by testing and the specific pollutants are identified, mitigation and remediation measures can begin.

Mitigation Measures

Vapor intrusion mitigation aims to reduce the transmission of these harmful vapors to protect the building’s occupants.

These measures are:

• Physical barriers: This includes multiple layers of chemically resistant sheeting or coating installed between a foundation and the source of the contamination
• Sub-slab depressurization: A fan is installed in an excavated space to trap vapors below a building’s concrete slab or ideally draw them away from the building entirely
• Active elimination: Fans are installed around a building or in the occupied space to prevent harmful levels of vapor from accumulating.

Remediation Measures

Ideally, part of eliminating vapor intrusion includes remediation, which is the removal or containment of the source of the pollution. However, this might not be possible if the source is on adjacent property or in a groundwater reservoir.

Remediation often involves the removal—or treatment in place—of large amounts of soil. An environmental services specialist can advise you on the options.

What’s Next?

Most likely, mitigation and remediation will only be able to lower vapor contamination to an acceptable or permissible level rather than fully eliminating it.

Once environmental specialists have confirmed that the mitigation and remediation strategy has worked, regular testing will still need to be carried out to make sure levels remain low. Initially, testing may take place every month, but eventually, scale back to once a year or less.

It’s important to work from the beginning with reputable environmental hygiene specialists who can:

• Carry out effective testing
• Design and implement a mitigation/remediation strategy
• Follow through with post-intervention testing and evaluation

Breathe Easier With Total Environmental Concepts

At Total Environmental Concepts, we take indoor air quality very seriously. We offer the knowledge and experience to develop thorough mitigation and remediation strategies for your property, including targeted pilot projects that can save time and money.

Our specialists are ready to provide effective testing and ongoing project support, plus guide you through the accompanying regulatory and compliance frameworks.

Click below to learn more about how we can help improve air quality in your building.