What mechanism typically causes the most radon entry into homes?

Radon entry into homes is primarily caused by pressure differences between the outdoor environment and the indoor space. In most cases, homes create a vacuum effect due to various factors such as heating systems, exhaust fans, and even stack effects, where warm air rises and creates negative pressure at lower levels, like basements. This negative pressure can draw radon gas from the soil into the home through the foundation and other pathways.

The mechanisms that enhance this draw include the natural construction of buildings, their proximity to radon sources in the ground, and how HVAC systems operate. Radon gas naturally emanates from uranium and radium found in soil and rock, and when the pressure inside the house is lower than that in the soil gas, the radon is pulled indoors. This process is a significant pathway for radon entry and underscores the importance of monitoring and mitigating radon levels in homes to ensure a safe living environment.