Under what circumstances should a long-term radon test be performed after an initial short-term test?

Conducting a long-term radon test in the same location as the initial short-term test during heating season conditions is essential for a few reasons. First, short-term tests can vary in their results based on environmental factors such as temperature, humidity, and ventilation. Radon levels can fluctuate significantly due to these variables, and winter heating systems can change airflow patterns and indoor air pressure, potentially affecting radon concentrations.

Performing a long-term test allows for a more accurate assessment of radon levels over time, typically spanning a minimum of 90 days. This longer duration provides a comprehensive view of the radon exposure that occupants would experience, as it averages out short-term fluctuations. Additionally, testing during the heating season is particularly important because many homes exhibit higher radon levels when they are closed up and heated during colder months.

By conducting the long-term test in the same location as the initial short-term test, you can compare the results more effectively and determine whether radon mitigation is necessary based on a more stable measure of radon over time rather than a snapshot that the short-term test provides.