Your radon test results are in. The report shows a number — but what does it mean, and what should you do next? Here's a plain-language guide.
What Is pCi/L?
Radon levels are measured in picocuries per liter (pCi/L) — a unit that describes the concentration of radon gas in the air. One picocurie is a tiny amount of radioactivity, and the "per liter" refers to the volume of air tested.
The average indoor radon level in U.S. homes is about 1.3 pCi/L. Outdoor air typically measures around 0.4 pCi/L.
The EPA Action Level: 4.0 pCi/L
The U.S. Environmental Protection Agency recommends taking action to reduce radon in your home if your level is 4.0 pCi/L or higher. The EPA also suggests considering mitigation for levels between 2.0 and 4.0 pCi/L — especially if you spend a lot of time in the tested area.
Radon Level Reference
Illinois Regulations
Illinois regulates radon mitigation under IEMA 422.150. The state requires that mitigation systems be installed by certified mitigators and that systems follow approved design standards. This protects homeowners from improper installs that could fail or create other hazards.
What To Do If Your Level Is Elevated
If your result is at or above 4.0 pCi/L, the next step is to contact a certified mitigation contractor. They'll assess your home's construction (basement slab, block walls, crawl space) and design a system — typically sub-slab depressurization — that creates negative pressure under the foundation, drawing radon out before it enters your living space.
Most installs are completed in a single day. A post-mitigation verification test (usually conducted 24 hours after install) confirms that levels have dropped.
Ready to Fix It?
If your results are elevated, ARS can typically schedule a mitigation install within a few days.