Which of the following statements is true regarding ASD systems?

The statement that ASD systems create a vacuum that prevents radon ingress is accurate because the primary function of Active Soil Depressurization (ASD) systems is to reduce radon levels in buildings by creating a negative pressure zone beneath the structure. This vacuum effect helps to draw radon gas from the soil and directs it outside before it can enter the living spaces. By using a fan to maintain this negative pressure, ASD systems effectively prevent radon from accumulating indoors, ensuring a safer environment for occupants.

Other statements may suggest misconceptions about ASD systems. For example, while structural changes can enhance their effectiveness, significant alterations are not necessarily required to implement an ASD system. Moreover, ASD systems typically rely on a fan to maintain proper airflow and pressure differentials; therefore, they are not as effective without this component. Lastly, ASD systems can be utilized in both new constructions and existing buildings, demonstrating their versatility in radon mitigation approaches.