Is testing a building site before construction considered a reliable predictor of indoor radon levels?

Testing a building site before construction is generally considered not reliable for predicting indoor radon levels. The primary reason for this is that radon levels can fluctuate significantly based on a variety of factors such as building materials, ventilation, and the specific design of the building itself.

Radon is a naturally occurring radioactive gas that can seep into buildings from the ground. Once construction occurs, various changes can affect how radon enters the structure or how it is ventilated. For instance, how the building is oriented, its foundation type, and the presence of barriers or mitigative measures can all dramatically alter radon entry points and concentrations.

Moreover, radon levels can vary even within different areas of a site due to soil composition, geological formations, and seasonal weather conditions. Therefore, while pre-construction testing can provide some insight into potential radon concerns, relying solely on those results to predict indoor levels post-construction can be misleading. It is essential to conduct radon testing after construction and during occupancy to obtain an accurate understanding of indoor radon levels.