Conceptually, a sub slab depressurization system is quite simple.
A PVC pipe is installed through the floor slab of a building basement and vented outside of the building or through the roof. A blower or fan is placed in the pipe that, when in operation, applies a vacuum to the subsurface of the building. This vacuum captures vapors from beneath the floor and sends them up the pipe to the atmosphere, where they dissipate. Depending on the chemical, the concentrations, and the flow rate, a treatment unit (typically granular activated carbon) may be used to clean the air before discharge. These systems are sometimes referred to as an Active Exposure Pathway Mitigation Measure or AEPMM.
A site investigation and engineering analysis should be performed as part of the design and operation of the SSDS to determine the location and concentrations of the chemicals in the subsurface, how many extraction points are required, and what flow rate and vacuum is needed to ensure full protection. When properly designed, installed, and operated, these systems are fully capable of rendering indoor air concentrations to below detectable levels – ensuring the safety of building occupants.