What is the maximum acceptable relative percent difference (RPD) for results less than 4 pCi/L?

In the context of radon measurement, the maximum acceptable relative percent difference (RPD) refers to the permissible variation in results obtained from different measurement methods or devices. For radon levels less than 4 pCi/L, the recognized standard specifies that the relative percent difference should be no greater than 67%. This allows for a significant margin of variability in measurements when radon concentrations are at lower levels, acknowledging the challenges inherent in accurately measuring low radon concentrations due to potential background noise and other environmental factors.

It's important to understand that this higher threshold of 67% is specifically designed to account for the uncertainty associated with low-level radon readings, as measurements can be less stable and more susceptible to fluctuations. Hence, in situations where readings are under 4 pCi/L, allowing a relative percent difference of up to 67% is deemed acceptable within the standards for radon measurement.