What is a significant factor in determining the seasonal variation of indoor radon levels?

Seasonal variation of indoor radon levels is significantly influenced by temperature differences due to the mechanics of how radon gas enters buildings. Radon, a radioactive gas that originates from the decay of uranium in the soil, infiltrates through cracks and gaps in the foundation and walls.

During colder months, buildings often experience more closed and stable conditions, where heating systems create a difference in air pressure between the inside and outside of a structure. This can enhance the draw of radon gas into the building, leading to higher indoor levels. Conversely, warmer temperatures tend to result in more ventilation and air exchanges, as windows and doors are opened to let in fresh air. This increased airflow can dilute the concentration of radon indoors.

While humidity levels, ventilation practices, and groundwater table levels can have some impact on radon concentrations, the primary driver of seasonal variations tends to be temperature differences, due to their direct effects on air pressure and building circulation. Therefore, understanding how temperature affects air exchange and pressure differences is crucial when assessing indoor radon levels throughout different seasons.