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Environmental Health and Safety Blog | EHSWire

Vapor Intrusion Air Sampling…Getting the Big Picture

Posted by Shivi Kakar

May 29, 2010 11:18:04 PM

Dale Wilson, CIH, LEED AP

Vapor Intrusion
“Vapor intrusion refers to this migration of volatile chemicals from the subsurface into overlying buildings.”  Vapor intrusion (VI) air sampling is a method to evaluate if chemical vapors are entering a building due to contaminated soil or groundwater that is on or adjacent to the property on which the building is built. In order for vapors to enter a building from the soil or groundwater there have to be pathways such as  cracks in the foundation, openings around piping used for mechanical, pluming, and electrical systems, groundwater entering the basement just to name a few. Once vapors are in a basement or crawlspace, there have to be additional pathways for the vapors to enter the first floor occupied space. 
When it comes to vapor intrusion understanding “why it is happening” is just as important as understanding “what is happening”.

What is Vapor Intrusion?

“Vapor intrusion has become a significant environmental issue for regulators, industry leaders, and concerned residents. Degradation of the indoor air quality can cause fear and anxiety among building occupants, businesses, and other property owners.”

A Vapor Intrusion Project

Recently, Emilcott was hired to review vapor intrusion air sampling data collected by another consultant.  The building site was a large commercial property that was mostly composed of office space, but there was also an onsite daycare center.  After collecting data for several years, the vapor intrusion had not been resolved. 

After reviewing all the data, we made a site visit to help us understand what was contributing to the continued and increased vapor concentrations -- both in the basement of the building, which was used for storage, and in the first floor daycare center.   

Our initial site visit revealed multiple pathways that permitted vapors to enter the basement and additional pathways that permitted vapors to enter the first floor occupied space.  It was clear that the owner’s other consultant had focused on What Is Happening through continuous air sampling without understanding the dynamics of Why It Is Happening.  Based upon

  • An analysis of the collected air monitoring data,

  • A thorough site inspection, and

  • An understanding of vapor intrusion causes and migration,

we were able to propose a step-by-step procedure to protect the client’s building and occupants. In addition, by including the client in the process, the client stated that they had learned more about the building from our visit than they had over the several years of data collection.

Vapor Intrusion – A Way Out

When reviewing a VI problem with a building owner or property manager, indoor air quality consultants should have answers to these basic questions to fully understand the problem and suggest a remediation solution:

  1. What are the volatile chemicals that we are dealing with?

  2. What are the risks of short-term and prolonged exposure to these chemicals?

  3. Why and where are they getting into my building?

  4. Can I stop the VI chemicals from getting in?

  5. If I can’t stop the VI chemicals from getting in, what are the alternatives?

Interrupting and sealing the pathways is the only way to prevent building occupants from exposure to vapors. 

For our client the process of sealing pathways has been accelerated and should be complete in a few weeks.  With the complete understanding of vapor intrusion What? and Why?, a plan to seal the pathways between the ground and the basement, and the basement and the first floor, may reduce the occupants’ exposures to the vapors and avoid any increased levels of regulatory oversight and accelerated response actions.

Have you experienced a vapor intrusion problem that remains unresolved or puzzled the experts? Do you have questions about indoor air quality issues and evaluation techniques and best practices? Please share your story or questions below and we’ll respond quickly.

Topics: indoor air quality, General Industry H&S, Construction H&S, Air Sampling, environmental air monitoring, Public Safety

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