(This is the third part of our vapor intrusion blog series. Catch up on Part I and Part II.)

Vapor intrusion mitigation aims to eliminate or reduce human exposure to impacted indoor air due to contaminated subsurface soil vapors. These methods are designed to eliminate or reduce the migration of vapors (e.g., sub-slab depressurization, building pressurization, or vapor intrusion barrier), or treat (e.g., indoor air purifiers, increased ventilation) vapors already inside a structure. The goal is to ensure that, after testing, any contaminant levels detected inside the structure post-mitigation are within acceptable levels.

Vapor intrusion barriers and their implementation bridge the construction world, where organized chaos is standard practice, and the environmental world, where risk is calculated based on soil gas concentrations in the parts per billion. While many products are available, the vapor intrusion barrier industry does not have established performance, installation, and quality assurance standards. This can be confusing for regulators trying to protect human health and, in turn, for consultants seeking regulatory approval.

The challenges of regulation and consistent standards

Regulators appear to be in flux while operating under the "guidance" moniker. At present, guidance works differently from state to state, some being more prescriptive than others, but in general, a regulator's role is to protect human health. This often translates into requirements that may err on being too lax or overly conservative, and these will differ from state to state.

Regulations are essentially situated at the crossroads between the environmental and construction worlds. There is guidance in place, but there is also industry practice. What is widespread in one state is not necessarily understood and accepted in another. This creates a form of “shadow regulation” where attorneys and banks will be to fall back on what the industry dictates to protect any real or perceived liability. It is easy to see where this can be challenging for all parties involved!

The main hurdle for regulators is that they often remain purely in the environmental world, and while that is important, the construction aspect is often overlooked or not fully understood. Yet with any form of mitigation, it needs to be installed properly and the correct installation process requires more understanding from the regulatory community.

To overcome the lack of clarity during the construction process, regulators often rely on strenuous post-construction monitoring, as most rely on indoor air sampling to demonstrate system effectiveness. Screening out background sources can be overly time-consuming and costly for building owners. In a newly constructed building, building materials are often full of solvents and other constituents that might lead to a false positive and trigger additional testing.

Instead, a more pragmatic approach should be taken to construction planning and oversight. The best mitigation plan can be compromised if it is not installed correctly. If regulators took the same interest in implementing these systems as they do in defining risk, the entire industry would benefit.

While there are no national standards yet, there is precedent for this concerning methane mitigation in Los Angeles. Here, full-time construction oversight is required when methane barrier systems are installed. The Los Angeles Department of Building and Safety Methane Mitigation Standards provide information describing the installation procedures, design parameters, and test protocols for the methane gas mitigation system.


In an ideal world, more regulations should be required on the implementation of vapor intrusion mitigation systems(VIMS).

  • Minimum testing requirements (puncture resistance, tensile strength, adhesion to concrete, etc)
  • Chemical resistance testing
  • Detailed system design
  • Field quality control and assurance
  • Formal documentation of the installation process

While all trades navigate evolving standards, it is paramount to work with a trusted vapor intrusion barrier manufacturer. With the right partner, QA/QC, custom detailing where needed, testing, and approved products as well as a proper warranty should be in place.

EPRO has a wide range of vapor intrusion mitigation systems, and we can work with you to wholly protect any building envelope at on any site at any location.