Radon Retest Umbra

When I bought my first house in St. Charles County back in 2006, the radon test was just another line item on the closing checklist. The inspector placed a small charcoal canister in the basement, left it there for a few days, and mailed it off. The result came back at 3.1 pCi/L, below the EPA Action Guide of 4.0 pCi/L. I signed the papers, moved in, and never thought about radon again. That was a mistake. Years later, after a minor basement flood, I decided to test again j