What factor draws radon into homes from the surrounding soil?

The factor that draws radon into homes from the surrounding soil is primarily air pressure. Radon is a radioactive gas that is produced naturally from the decay of uranium in soil and rock. When the air pressure inside a home is lower than the air pressure in the soil surrounding it, a pressure differential is created, which allows radon to be drawn into the building through cracks and openings.

This phenomenon is influenced by the fact that homes often have reduced pressure indoors compared to external soil pressures, especially during activities like the use of exhaust fans, heating and cooling systems, or during air circulation changes. Thus, it is the pressure difference that facilitates the movement of radon gas from the ground into the home environment, making air pressure the key factor in this process.

As for temperature, humidity, and soil composition, while they can play roles in radon levels, they do not directly create the pressure differentials that draw radon into homes as air pressure does.