What is the primary consideration before conducting tests for radon measurement?

The primary consideration before conducting tests for radon measurement is the establishment of closed-building conditions. This condition is crucial because it ensures that the indoor environment remains stable and representative during the measurement period. In a closed-building scenario, windows and doors should be closed for a certain duration before and during the testing, typically for a minimum of 12 hours. This prevents outside air from diluting radon levels, which can lead to inaccurate or misleading measurements.

By adhering to closed-building conditions, testers can obtain reliable data that accurately reflects the radon concentration within the home or building being tested. This is fundamental in understanding potential radon exposure and assessing whether mitigation is necessary.

While factors such as the time since the last measurement, the specific location of the measurement device, and the type of radon testing device do play roles in the testing process, they do not hold the same level of priority as ensuring closed-building conditions. These other factors can influence the results but cannot substitute for the need for controlled testing circumstances to yield valid results.