Which natural phenomenon can lead to variations in indoor radon levels?

Barometric pressure changes due to severe weather are known to influence indoor radon levels. When the barometric pressure drops, which often occurs before a storm, the pressure differential can cause radon gas, which originates from the ground, to be drawn into buildings more readily. This is particularly relevant because radon is a naturally occurring radioactive gas that seeps from the earth's crust and can accumulate in enclosed spaces, especially in basements or lower levels of homes.

Understanding this relationship is important for radon mitigation specialists as it highlights how external environmental factors can affect indoor air quality. By recognizing the connection between barometric pressure and radon levels, mitigation strategies can be better tailored to address potential spikes in radon concentration during stormy conditions.

The other options involve factors that do not have a direct correlation with radon levels. Regular maintenance of HVAC systems, while important for overall air quality, does not specifically influence radon gas entry. Air purifiers can improve air quality by removing particulates and other pollutants, but they are generally ineffective against radon gas itself, which requires specific mitigation approaches. Increased household water usage may create vapor release of radon from water sources but does not inherently affect the indoor air concentration of radon like barometric pressure changes do