During which months might radon concentrations be most hazardous in homes with return air ducts under concrete floors?

Radon concentrations can become particularly hazardous when the heating or cooling system fan is consistently active because it creates negative pressure in the home, which can draw radon gas from beneath the foundation into the living spaces. In homes with return air ducts under concrete floors, the air exchange system is crucial in influencing air movement. During winter months, when heating systems are more frequently used, the fan can operate continuously, facilitating the upward movement of radon from the ground.

This scenario is exacerbated if the home is sealed tightly to conserve heat, as limited ventilation can lead to an accumulation of radon gas. As radon is a naturally occurring, radioactive gas that emanates from the ground, any condition that increases its entry into the home, particularly under the circumstances described, poses a heightened health risk. Thus, the consistent activation of the heating or cooling fan plays a pivotal role in potentially elevating radon concentrations indoors.