Which type of ACD is biased towards the end of the testing period?

The correct choice indicates that both types of ACDs (Active Charcoal Detectors) exhibit a bias towards the end of the testing period due to their inherent design characteristics.

Both Open Faced ACDs and Diffusion Barrier ACDs are designed to absorb radon gas over a specified exposure period. However, the behavior of these devices can lead to variations in accuracy based on when they are exposed to radon. Typically, during the later stages of the testing period, there may be an increase in the accumulation of radon decay products, potentially skewing the results towards higher concentrations of radon due to the cumulative effect of longer exposure.

This bias can be more pronounced in specific detection methods, where the amount of radon measured can reflect fluctuations in radon levels that occur over time. Therefore, both types of ACDs can be affected similarly by the timing of the exposure, leading to results that are biased toward the end of the testing period, rather than uniformly across the entire duration of the test.

Understanding this concept is vital for technicians as it emphasizes the importance of consistent testing practices and interpretation of results within the timeline of exposure.