Radon Mitigation & Testing
In Markham, IL

Cook County is in EPA Radon Zone 2, moderate radon potential. The EPA predicts average indoor screening levels between 2.0 and 4.0 pCi/L. Many homes here still test above the 4.0 pCi/L action level, so the EPA recommends every home be tested. Cook County is in EPA Zone 2, the middle of the three predicted levels. 43 of the 102 counties in Illinois share that rating. The only way to know your home's actual level is a radon test.

The EPA action level is 4.0 pCi/L, at or above that, the EPA recommends having a mitigation system installed. Because there is no known safe level of radon exposure, the EPA suggests considering mitigation between 2.0 and 4.0 pCi/L as well. The World Health Organization recommends acting at 2.7 pCi/L.

You have two options: hire a radon measurement professional from this page for a precise 48-hour monitor test, or use a do-it-yourself test kit from a hardware store or your state radon program. Short-term tests take 2–7 days; if the result is 4.0 pCi/L or higher, confirm with a follow-up test or move straight to mitigation.

Most single-family radon mitigation systems cost between $800 and $2,500 installed, with typical jobs around $1,200–$1,800. Those are national figures; we do not publish a price for Markham, because the number that matters is the one a contractor gives you after looking at your foundation. Price depends on foundation type (basement, slab, crawlspace), house size, and how the piping has to be routed. 235 companies cover Markham within about 50 miles, and the 25 below are a selection of them. Three quotes is a reasonable ask rather than an imposition, and prices for the same job vary more than most homeowners expect.

The standard fix is active sub-slab depressurization: a sealed pipe is inserted through the foundation floor, and a continuously running inline fan pulls radon-laden soil gas from under the house and vents it above the roofline, before it can enter your living space. Systems typically reduce radon by 80–99%, run on about as much electricity as a light bulb, and include a manometer so you can see it's working.

It depends on the state. Some states license anyone who measures radon for a fee or installs mitigation systems; others leave it to voluntary national certification. Certification and license details change over time, so check any company's current standing with the Illinois radon office at (217) 785-9989 before you hire.

Radon testing is a standard part of real-estate transactions in most of the country. Buyers: ask for a professional radon test during your inspection window, it takes about 48 hours. Sellers: testing (and mitigating if needed) before listing avoids surprises at closing. A mitigation system with documented low results is a selling point, not a liability.