What is the recommended action for windows and exterior doors during the testing period?

The recommended action for windows and exterior doors during the testing period is to keep them closed. This is crucial for obtaining accurate radon measurements, as open windows and doors can allow outside air to enter the testing environment, potentially diluting the concentration of radon gas present in the indoor air.

Radon testing aims to measure the radon levels as they would typically be in a home without interference from outside variables. Keeping windows and doors closed helps ensure that the results reflect the home's usual radon levels over the testing period. Any variability caused by air exchange with the outdoors could lead to misleading measurements and affect the overall assessment of radon levels in the home. Thus, maintaining a controlled environment during the testing is essential for reliable results.