If one radon measurement result is greater than 4 pCi/L and another measurement is less than 4 pCi/L, what should be done?

When faced with radon measurement results where one exceeds the action level of 4 pCi/L and the other is below this threshold, the most prudent course of action is to re-test, particularly in the context of significant disparity between readings. If one measurement is double the other, this indicates a notable variation in radon levels that could be influenced by factors such as air pressure changes, time of year, or even the specific location within the property where the measurements were taken.

The recommendation to retest serves to ensure that the results are consistent and accurate, providing more reliable data for making decisions about potential radon mitigation. If the higher reading is indeed double the lower reading, that elevation is cause for concern and would typically warrant a stronger recommendation for mitigation actions to protect health and safety. This cautious approach emphasizes reliability and consistency in measurement, reflecting best practices in radon testing and mitigation strategies.

Other approaches, such as simply accepting the higher reading or averaging the two, may not accurately reflect the actual radon levels present and could potentially lead to insufficient action regarding mitigation. In cases of conflicting readings, further testing is vital to determine the real risk posed by radon exposure.