Radon is the second leading cause of lung cancer in the U.S. Radon levels fluctuate due to seasonality as well as weather. It is possible that the results from radon test you purchased when you bought your home is no longer valid. According to the EPA, the maximum “acceptable” level of radon is 4.0 PCI/L, but even that level is not “safe”, per se. The EPA strongly recommends you consider radon mitigation between levels 2.0 and 4.0.Radon Levels fluctuate over time, and while the EPA recommends that you take an average over 48 hours’ worth of radon measurements to determine if the radon is above 4.0 PCI/L, we notify you of the individual measurements every fifteen minutes.