What is a condition that warrants re-testing for radon levels?

Re-testing for radon levels is warranted when an addition to a home is completed. This is because any significant structural modifications can alter the airflow and the foundation's integrity, potentially affecting radon levels inside the home. Adding a room or expanding living space can create new pathways for radon to enter or change how air circulates, which may lead to higher levels of radon even if previous measurements were within safe limits.

It's important to ensure that radon levels remain safe after structural changes, as the risks associated with prolonged exposure to high radon levels are well-documented. Therefore, following any major alterations to a property, such as building an addition, re-testing is a prudent measure to guarantee that the indoor air quality remains safe for occupants.