Vapor intrusion is the migration of vapor-phase contaminant chemicals from a subsurface source in an overlaying building or structure. The objective of many vapor intrusion investigation professionals is to be able to detect possible pathways for contaminant vapors and their location within the building or structure. Understanding the potential pathways helps to identify risks. A solid understanding of potential pathways informs the client selling the building to potential tenants, who need to be able to live and function within the building without exposure to health risks. Here are four key things to know about vapor intrusion.

It’s A Process

Number one, vapor intrusion investigation and mitigation is a process. Vapor intrusion science requires in-depth investigation. It is not a field which requires only one test to say whether a building does or does not have vapor intrusion. In-depth investigation includes options based on the site and its environment. The in-depth investigation must determine what type of gases are emitting through the cracks, where the origin and the major intrusion pathway are  located. Additionally, the consultant’s next step is contacting the local government environmental representative to confirm the state’s regulatory guidelines and to receive approvals for developing the site. Even after all the preparation work and investigations, the environmental consultant will have to develop a design to cover the exact needs of the site. There is no quick way to handle vapor intrusion. Each site must be evaluated thoroughly to move onto the next step to mitigate the effects of the vapor intrusion.

Recognize Outside Factors

Though thorough investigation is necessary to get an accurate reading of the site, the results may not be complete. At times investigations or screenings of a site will pick up additional vapors from the testing area or concentrated in one single area to indicate contaminants present. These readings could be caused by a number of factors, even common household appliances on site. For example, if an industrial adhesive product like E6000 glue is located anywhere in the screening area, there will be a significant increase in TCE indicated in the testing, which would easily skew the readings. So, Before any screening can be performed on site, investigators should go through the site with a close eye looking for indoor VOC sources, like paints, cleaning supplies, or insecticides. For more information, visit the EPA’s website regarding the specific materials to look for in a site, along with other information to address VOC concerns is a great resource:

In a webinar with Land Science, and the Compound Specific Isotope Analysis (CSIA) Lab Director of Microbial Insights provides some tools to help distinguish whether the source of vapor-contaminated indoor air originates from the buildings subsurface or an indoor source.

There are other uncontrolled factors that could contribute to excessive readings, including spatial and temporal variability. Some examples of spatial variability factors to consider are soil types like gravel or sand, bedrock fractures, oxygen distribution in the soil, subsurface building structures and even surface features like pavement or water features. Each of these examples either provide a clear path for VOCs to reach the site or the groundwater or affect how quickly VOCs could reach the site. Examples of temporal variability include: wind speed and direction, barometric pressure, temperature inside or outside, precipitation, and ambient contaminants. These variables can affect how the screenings read the concentrations of VOCs at the site.

Solutions Are Site Dependent

Vapor mitigation professionals are also tasked with developing a solution based on the site’s conditions along with the state/federal regulations. Each site is different, so vapor mitigation often cannot be based on a plan used at a former site with similar conditions. The investigations unveil all the aspects of a site that determine what the remediation plan will be, including: soil types, weather patterns, gas distributions, subsurface conditions, as well as site goals and budget. Each one of these factors can impact the design of a vapor mitigation system, and each factor can yield different results.

Land Science is comprised of a team of vapor intrusion mitigation professionals who have the technical expertise and industry experience to make the most effective recommendations for our clients. Couple that with a range of innovative technologies that address a variety of site types, and the result is industry-leading vapor intrusion solutions that help public safety.

It’s a Growing and an Evolving Science

The final key idea behind vapor intrusion science that everyone should know, it is a growing and an evolving science. The reason vapor intrusion science came into existence was because of the avid use of VOCs—volatile organic compounds–as root zone fumigants and other applications in the 1950s. Surveys of landfill gas and radon exposure in the 1960s lead to the discovery of vapor intrusion in the late 1970s and was found to affect indoor air quality at heavily contaminated sites, which brought the full scope of regulatory attention.

However, at this point, scientists and regulators dismissed the concerns to homeowners due to the processes of dilution and attenuation as well as the ambiguous exposure standards and the fact that most vapor intrusion was found at major former industrial sites. Consequently, scientists began finding vapor intrusion inside residential homes and decided to facilitate public education by going door-to-door and providing information on the issue of vapor intrusion.

The increase in public awareness resulted in a rise of attention and studies regarding vapor intrusion through the 1990s to the 2000s, pushing states to start developing vapor intrusion protocols and ultimately causing the EPA to publish “Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from Groundwater & Soils.” Today 42 states have developed their own regulation system for vapor intrusion and the other 8 follow the EPA’s regulation system or deal with vapor intrusion on a case-by-case basis. The history of vapor intrusion has expanded over decades; from the introduction of VOCs in the 50s to the development of a national regulation standards in the 2000s, vapor intrusion science has gone through many changes and continues to develop. Those who work in the field of vapor intrusion must expect continuous changes, whether it be through regulation,  techniques, or emerging science on its effects.

This evolution has caused remediation companies notice and respond to the demand and serves to further develop the technology. For instance, Land Science, a division of REGENESIS® and a global leader of advanced vapor intrusion mitigation technologies, recently introduced TerraShield – a cutting-edge remediation technology which provides superior chemical resistance over any vapor barrier on the market today. Land Science also offers a full-suite of vapor intrusion barrier systems including Nitra-Seal, a proven vapor barrier system now improved with nitrile; and MonoShield, a chemically resistant and easy-to-apply barrier specifically designed as a preemptive solution for vapor intrusion at brownfield redevelopment sites and Retro-Coat, a chemically resistant vapor barrier coating system to properly protect existing structures from the threat of contaminant vapor intrusion . With solutions like TerraShield, Nitra-Seal, MonoShield and Retro-Coat being made available to vapor intrusion mitigation industry, this field is now poised to address the needs created by an increasingly demanding regulatory landscape.

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