What is the only permanent evidence device that can be recounted for results?

The correct choice highlights the Alpha Track Detector as the only permanent evidence device that can be recounted for results. Alpha Track Detectors are designed to measure radon levels over extended periods, typically 90 days to a year. They work by allowing radon gas to diffuse into a detection material, where it produces tracks that can be counted and analyzed later. This ability to store and recount data makes Alpha Track Detectors a reliable choice for long-term radon measurement.

In contrast, other options like the Charcoal Liquid Scintillation Device and Passive Collector are designed for short-term measurements and do not provide permanent records that can be re-evaluated after the initial reading. Active monitors continuously sample air and provide real-time data but do not produce physical evidence that can be recounted. Thus, the distinct functionality of the Alpha Track Detector sets it apart as the preferred method for obtaining permanent evidence in radon measurement.