What is the maximum acceptable Relative Percent Difference (RPD) for a collocated test if both devices record results under the action level?

The maximum acceptable Relative Percent Difference (RPD) for collocated radon measurement devices under the action level is 67%. This threshold is established to ensure that the results from different measurement devices are in close agreement, thereby affirming their reliability and accuracy when recording lower levels of radon.

In radon measurement practices, particularly when results are below the action level, it's critical to maintain a balance between sensitivity and practicality. Setting the RPD threshold at 67% allows for the inherent variability that might occur due to slight differences in device calibration or environmental factors while still ensuring that the measurements are sufficiently consistent for effective radon management decisions.

Understanding RPD and its role in ensuring accurate radon measurements helps practitioners maintain credibility in their testing processes and ensure safety in residential environments.