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How is a Sub-Slab Depressurization System Installed? {Infographic}

January 9, 2018

As regulations increase across the country regarding evaluating vapor intrusion pathways, so too is the need for proper mitigation systems.

The first step towards properly mitigating vapor intrusion involves sub-slab soil gas sampling to identify the levels assess the potential risk.  

If Vapor Intrusion is identified, and found to be above the screening levels, a mitigation system should then be put in place.  For existing buildings where vapor intrusion is identified, the most common mitigation system is the Sub-Slab Depressurization System (SSD). SSD systems are used to mitigate indoor vapors arising from subsurface contamination.

The EPA defines SSD technology as "a system designed to achieve lower sub-slab air pressure relative to indoor air pressure by use of a fan-powered vent drawing air from beneath the slab." Thus, even if there are holes, cracks, or other pathways between the building and the subsurface, vapors flow downward, not upward. Thus, a well-designed depressurization system prevents any toxic vapors from intruding above.*

See how this system is installed: