In the context of long-term testing, how are closed-building conditions treated for tests lasting more than 90 days?

In long-term radon testing, particularly for periods extending beyond 90 days, closed-building conditions are not mandated. This is primarily due to the nature of long-term tests, which are designed to evaluate the average radon concentration over an extended duration.

During this time, typical variations in humidity, temperature, and ventilation may naturally occur, making it impractical to maintain strict closed-building conditions throughout the entire testing period. This flexibility allows for more realistic evaluations of radon levels as they are likely to fluctuate based on daily and seasonal changes.

While it's beneficial to aim for a relatively stable environment to avoid extreme influences on readings in the early stages of testing, after 90 days, the focus shifts to the overall average rather than precise control over conditions. Thus, the approach regarding closed-building conditions is relaxed, reinforcing that they are not a requirement for long-term testing scenarios extending beyond this timeframe.