Active soil depressurization systems are primarily used when the main radon transport mechanism is what?

Active soil depressurization systems are specifically designed to mitigate radon intrusion from soil into buildings by creating a pressure differential that helps divert radon gas away from the structure. The primary mechanism at play in this scenario is air pressure differences, which can lead to radon being drawn into homes from the surrounding soil.

When outdoor air pressure is lower than the pressure inside the building, radon gas tends to flow into the home. Active soil depressurization systems work by installing a fan and a system of pipes that create a vacuum beneath the foundation of the building. This vacuum reduces the pressure in the soil, which effectively prevents radon from entering the home by maintaining a higher pressure indoors.

In contrast, while factors such as soil permeability, water movement, and temperature differentials can influence radon levels, they are not the primary mechanisms for radon transport that active soil depressurization systems are designed to address. Soil permeability can affect how easily radon migrates through the ground, but the active system's focus is on managing pressure differences rather than solely on the characteristics of the soil or moisture in it.