Which of these locations is an acceptable place to install an ASD fan according to the standards?

Installing an ASD (Atmospheric Depressurization System) fan on the exterior of the building is an acceptable practice as it allows for effective ventilation while minimizing the risk of indoor air contamination. By placing the fan outside, it ensures that the air being exhausted does not directly re-enter the living spaces, thereby enhancing the overall safety and effectiveness of the mitigation system. This design is practical as it helps to maintain negative pressure in potentially contaminated areas and allows for efficient removal of radon and other harmful gases from beneath the building.

Proper installation on the exterior can also facilitate maintenance and reduce noise levels in the living areas, contributing to occupant comfort. Moreover, this approach aligns with guidelines and standards that emphasize minimizing potential health risks associated with radon exposure.

In comparison to other locations, such as basements or crawl spaces directly beneath living areas, exterior installation avoids the risk of diluting or redistributing radon concentrations within the home. Conditional occupied spaces may not provide the same level of assurance for effective radon migration prevention as an exterior installed fan does.