Chemical vapor intrusion (VI) can be a significant health risk to building occupants in the proximity of soils and/or groundwater contaminated by volatile organic compounds (VOC emissions). The risk of soil vapor intrusion often dominates current investigations of environmental contamination. Also, vapor intrusion can have profound impacts on property developments and real estate transactions for properties adjacent to contamination. Yet, the vapor intrusion industry continues to evolve and the most effective and efficient solution to soil vapor intrusion is further debated.
As a former environmental regulator, my first experiences with vapor intrusion and sampling methods showed an industry clearly in its early stages. Government and Industry experts invest significant time and money researching these sampling methods. They also study the nature of vapor migration in preferential pathways and beneath structures.
In the 15 years that have followed those first vapor intrusion experiences, a consensus on representative sampling for a definitive determination of vapor intrusion indoor air risks remains elusive. In the absence of an agreement, the result is a range of variability in how such determinations are made. Frequently, there are debates regarding vapor intrusion risk to building occupants and the multiple iterations of sampling. Often, the sampling can take months or even years and cost thousands of dollars. All the while, the potential for occupant exposure continues.
Don’t debate, mitigate.
Protection from changing vapor intrusion regulations and best practices
The EPA’s VI guidance (EPA 2015) clearly states that pre-emptive mitigation can be an early action that protects building occupants. Mitigation also involves less disruption to the occupants compared to multiple iterations of indoor air sampling events.
Additionally, mitigation can generally be implemented relatively quickly and cost effectively in most structures and building types. While vapor intrusion and sampling practices continue to be regularly debated, soil gas mitigation techniques are well founded from over 30 years of radon mitigation.
Furthermore, national consensus-based standards developed by the American Association of Radon Scientist and Technologists (AARST), through the American National Standards Institute (ANSI), include a broad group of stakeholders with backgrounds spanning in radon, chemical vapor intrusion, state and federal regulatory agencies, and manufacturing. These standards, available for free at (http://standards.AARST.com), establish clear criteria for the design and implementation of soil gas mitigation solutions.
Ultimately, rather than debating yet-to-be-decided-upon vapor intrusion investigation practices, investing in the established science of mitigation saves time and money.
Don’t debate, mitigate.
VOC's, Radon, and Other Contaminants
Beyond the primary purposes of mitigating to eliminate intrusion of known VOC impacts, mitigation provides several secondary benefits. Active soil depressurization not only prevents VOCs from entering a structure, but also limits the intrusion of other soil gases, including water vapor, odors, pesticides, and radon.
A reduction in water vapor intrusion can significantly improve a structure both in comfort and in the reduction of potential mold development. Also, radon reduction is perhaps the greatest standalone reason for mitigating a property. Radon is found throughout the country and the leading cause of lung cancer among non-smokers. This radioactive gas is a known carcinogen that results in approximately 21,000 lung cancer deaths annually (https://www.epa.gov/radon/health-risk-radon). The current EPA action level for radon is 4.0 pCi/L, at which the risk for developing cancer is up to 1000 times greater than the cleanup standard for environmental contaminants. Besides VOC intrusion, all structures can benefit from active soil gas mitigation.
Don’t debate, mitigate.
Soil Vapor Intrusion Solution - Mitigation and Monitoring
Actively mitigating structures at the earliest indication of potential vapor intrusion risks utilizes well established and standardized techniques to immediately protect building inhabitants from suspected contamination. Although, mitigation can also protect inhabitants from radon and potentially improve the overall indoor air quality. Compared to ongoing, costly, and often inconclusive indoor air sampling events, active soil gas mitigation is quick, cost effective, and a definitive solution to vapor intrusion.
Additionally, modern advances for vapor intrusion monitoring now exist through telemetric technology. Continuous long-term monitoring for mitigation operation and performance reduces the need for costly and time-consuming sampling. With advanced monitoring equipment, such as the Vapor Sentinel Remote Monitoring system, mitigation can be monitored continuously, documenting any changes in data. 24/7/365 continuous monitoring protects stakeholders by protecting against possible liabilities and keeping building occupants from potential exposure.
Don’t debate, mitigate.
Want more information?
Frequently Asked Questions
Soil vapor intrusion is the movement of harmful vapors from contaminated soil or groundwater into a building above. It commonly involves volatile organic compounds, or VOCs, that migrate upward and enter through the foundation. It can pose health risks to occupants and affect property transactions near known contamination.
Sampling to prove vapor intrusion risk can take months or years and cost thousands, while occupants remain potentially exposed. EPA guidance recognizes pre-emptive mitigation as an early protective action. Mitigation is usually faster, less disruptive, and more definitive than repeated indoor air sampling, which is why we say, do not debate, mitigate.
Most systems use active soil depressurization. A fan creates suction beneath the building foundation and vents soil gas safely above the structure before it can enter. This proven approach is drawn from more than 30 years of radon mitigation practice and works in most structures and building types.
Yes. Active soil depressurization limits many soil gases at once, not just VOCs. It also reduces radon, water vapor, odors, and pesticides entering the building. Radon reduction is often the single greatest standalone reason to mitigate, since radon is a known carcinogen with an EPA action level of 4.0 pCi/L.
Soil gas mitigation follows national consensus standards developed by the American Association of Radon Scientists and Technologists through the American National Standards Institute. These AARST and ANSI standards set clear criteria for design and installation, and they are available at no cost from the AARST standards website.
Modern systems can be monitored continuously using telemetric technology such as the Vapor Sentinel remote monitoring system. Continuous, long-term monitoring documents system performance and any changes in data around the clock, which reduces the need for costly repeat sampling and helps protect occupants and stakeholders from liability.
