What do I do if a test result is less than 4 pCi/L?
If the result of an initial test measurement is below 4 pCi/L, a follow-up test is not necessary. Because radon levels change over time, you will want to retest every couple of years, especially if use patterns change or perhaps a lower level of the building becomes occupied or used more frequently. Renovations, changes in ventilation, earthquakes, settling of the ground beneath the building, and other changes may cause indoor radon exposures to change.
