Radon Testing and Mitigation: A Homeowner’s Complete Guide

Radon is a colorless, odorless radioactive gas produced by the natural decay of uranium in soil and rock. It seeps into homes through foundation cracks, sump pits, and slab penetrations, and it concentrates in the lowest occupied level. The EPA attributes roughly 21,000 lung-cancer deaths per year in the United States to radon exposure, making it the leading cause of lung cancer among people who have never smoked.

The only way to know your level is to test. Short-term tests (charcoal or electret kits) run 2–7 days and give a fast screening result; long-term tests (alpha-track detectors) run 90+ days and better reflect your year-round average because radon levels swing seasonally. For the most reliable picture, the EPA recommends placing the test in the lowest lived-in level of the home, with windows and exterior doors closed for at least 12 hours before and during a short-term test.

Results are reported in picocuries per liter (pCi/L). The EPA action level is 4.0 pCi/L: at or above that figure, you should mitigate. The agency also suggests considering mitigation between 2 and 4 pCi/L, because there is no known safe level of radon — risk falls continuously as the concentration drops. The World Health Organization uses a lower reference of 2.7 pCi/L (100 Bq/m³).

The standard fix is an active soil depressurization (ASD) system: a contractor seals major entry points and installs a sealed PVC pipe that draws soil gas from beneath the slab and vents it above the roofline using a continuously running inline fan. A well-designed ASD system typically reduces indoor radon by 80–99% and, in most homes, brings levels below 2 pCi/L. A post-mitigation test confirms the result.

Choose an NRPP- or NRSB-certified mitigation professional. Certification verifies the contractor has been trained and tested to AARST/ANSI consensus standards (such as SGM-SF for single-family homes). Every contractor listed on HomeAllClear is shown with its credential so you can confirm it before requesting a quote. Re-test every two years and after any major foundation or HVAC work.