Vapor mitigation is a segment of the environmental industry that is maturing rapidly. There are many new technologies emerging to prevent vapor intrusion which safely and effectively address a variety of structures. Vapor mitigation methods are classified as either passive or active.

Passive vapor mitigation involves barriers installed in existing buildings or pre-construction to prevent the entry of chemical vapors. Passive vapor barriers are installed in a variety of structures including homes, businesses, or other industrial buildings and are generally a cost-effective approach, making passive vapor barriers the most common and appealing method for vapor mitigation. One approach available for existing structures is to seal or fill the cracks in a building’s floor slab or around pipes and utility lines in walls. Retro-Coat™ is an example of a vapor barrier coating system that protects existing structures and can be customizable to fit the unique needs of the structure. Another method of passive mitigation is installing a venting layer in a basement which pushes harmful vapors toward the sides of the building and then outdoors. A third vapor barrier option involves installing a barrier made up of strong plastic-like sheets placed beneath a building’s foundation or in crawl spaces. At Land Science, Geo-Seal® is a safe and proven vapor barrier system comprised of three intensive layers designed and installed in newly constructed buildings. Scientifically tested to provide the highest level of protection from vapor intrusion, Geo-Seal is the trusted source for many environmental professionals and developers across the US and Canada.

Active mitigation is the practice of changing the pressure between the sub-slab and the inside of the building to keep chemical vapors out. This method is considered to be highly effective but is usually more expensive than a passive system due to the high cost of maintenance. A sub-slab depressurization (SSD) system involves the use of a blower or electric fan. A suction pit is installed in the sub-slab allowing for contaminated groundwater vapors to rise to the surface and into the structure. The electric fan or blower draws out the chemical vapors and releases them outside the building’s structure. This system is highly effective and is used for radon and VOC control. Another active mitigation system available involves building pressurization which adjusts a building’s heating, air-conditioning, and ventilation system indoors relative to the pressure in the sub-slab. When positive pressure is introduced inside the building, it prevents chemical vapor from entering the building. This method tends to produce a high energy cost and is considered to be less-effective compared to SSD.

Additionally, there are solutions developed using both passive and active methods. For example, a passive system can be designed to become active if needed and is offered as one of the options available through Land Science. Vapor Vent™ goes above and beyond by providing cost savings, speedy installation, and other performance benefits.

Sources:
http://www.newmoa.org/cleanup/cwm/vapor/FolkesPresentationApril2006.pdf

https://nepis.epa.gov/Exe/ZyNET.exe/P100F9XC.TXT

https://www.trcsolutions.com/writable/images/TRC-white-paper-Vapor-Intrusion-FINAL-March-2016.pdf

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