What is a key reason for conducting a post-mitigation test?

Conducting a post-mitigation test is essential primarily to identify the effectiveness of the mitigation system installed to reduce radon levels in a building. After mitigation measures have taken place, such as the installation of a radon mitigation system, it is crucial to verify that these measures are functioning properly and successfully lowering the radon concentration to acceptable levels. This testing provides reassurance to homeowners and occupants that their indoor air quality has improved and that the radon levels are now below the action level recommended by health agencies.

Although the other options touch on related concepts, they do not capture the primary purpose of post-mitigation testing. For instance, while the operation of the fan may be part of a broader assessment, the key objective remains the validation of the entire mitigation effort's success. Similarly, this testing is not solely mandated by legal requirements; rather, it is a standard best practice in radon management to ensure safety and effectiveness. Finally, measuring local radon levels is an important aspect of understanding radon risk in an area, but it is separate from the specific goal of determining the operational status of a specific mitigation system in a tested property.