What conditions must be met prior to using short-term test results for mitigation decisions?

Short-term radon testing is a common method for assessing radon levels in a building over a limited time frame, typically from 2 to 90 days. For these results to be reliable and actionable, closed-building conditions need to be implemented. This means that the windows and doors should remain closed for at least 12 hours before and during the test, and that the HVAC system should be in a normal operating mode.

The reason for requiring closed-building conditions is to minimize fluctuations in radon concentration that can occur due to external weather conditions, seasonal changes, or ventilation from open windows and doors. If a test is conducted under these closed conditions, it provides a more accurate representation of the radon levels present in the home or building as they would typically be experienced by occupants. This accuracy is essential for making informed decisions regarding mitigation efforts.

The other options do not meet the necessary criteria for accurate radon testing. For instance, if closed-building conditions are considered optional, the reliability of the test results could be compromised. Similarly, open-building conditions would allow outside air to influence the radon levels detected, leading to potentially misleading results. Testing detectors in multiple rooms, while sometimes beneficial for comprehensive evaluation, does not substitute the need for closed conditions during a