During short-term testing for radon, what condition must be maintained in the house?

Maintaining a closed condition in the house during short-term radon testing is crucial for obtaining accurate results. When windows and doors are kept closed, it reduces the amount of outdoor air entering the home, which can dilute radon levels. This ensures that the test accurately reflects the radon concentration present within the specific environment of the house, without interference from external air that may be radon-free or has lower radon levels.

A closed condition also helps in capturing the radon gas that potentially accumulates in lower areas of the house, such as basements, where radon is more likely to be present due to its geological origins. Open or ventilated conditions can lead to a significant underestimation of radon levels, as any radon that might otherwise accumulate inside can quickly disperse, skewing the test results. Thus, keeping the house closed is essential to achieve reliable and valid measurements of radon concentrations during short-term testing.