Radon Blog
Home Health, Safety
Radon and your home: what every Illinois homeowner needs to know
It's invisible, odorless, and naturally occurring — and it may be quietly building up in your home right now.
By Plus Ultra Home Inspections
📌 Key Stats: 21,000 estimated lung cancer deaths per year linked to radon (EPA) · #2 leading cause of lung cancer in the U.S., behind smoking · 4 pCi/L is the EPA action level — fix your home if results are at or above this.
What is radon?
Radon is a colorless, odorless, radioactive gas produced by the natural breakdown of uranium and radium in soil. Because uranium is found widely in the ground, radon is essentially everywhere — but problems arise when it accumulates inside an enclosed space like a home.
As warm air rises and escapes through a home's upper openings, the lower pressure draws air in from the surrounding soil. Radon enters through cracks in foundation floors and walls, hollow-block walls, and openings around floor drains, pipes, and sump pumps. The key question for any home is never whether radon is present, but how much.
Why does it matter for your health?
Once inhaled, radon undergoes radioactive decay inside the lungs, releasing bursts of energy known as alpha particles. These particles can damage lung tissue at the DNA level — and that damage can eventually lead to lung cancer. For non-smokers, radon is the single leading cause of lung cancer. The risk is compounded for smokers.
One important nuance: not everyone exposed to elevated radon levels will develop lung cancer. But because the risk is real, cumulative, and silent — with cancer potentially not appearing for many years — testing is the only responsible way to assess your exposure.
How is radon measured?
Radon is measured in picoCuries per liter of air (pCi/L). To put the numbers in context:
Level What it means 0.6 pCi/L Average outdoor air level in Illinois 1.3 pCi/L National indoor average 2–3.9 pCi/L Elevated — retest with a long-term detector 4 pCi/L+ EPA and CDC action level — mitigation recommended
How do you test for radon?
There are two main testing approaches:
Short-term test (2–7 days) — A detector is placed in the lowest livable area of the home. Once the period ends, it's sealed and mailed to a certified lab. Results typically arrive within two weeks. Before starting, close exterior windows and doors for 12 hours and keep fans off for the duration of the test.
Long-term test (3 months–1 year) — An alpha track detector provides the most accurate picture of your home's yearly average radon level. This is the preferred method for ongoing monitoring and for confirming results after an initial short-term test.
For real estate transactions in Illinois, it is recommended to hire a professional licensed by the Illinois Emergency Management Agency (IEMA) to conduct radon testing. Test kits are also available through public health departments, retail stores, and by mail.
What do the results mean — and what comes next?
Result Recommended action Below 4 pCi/L No action needed. Retest in two years. 4–8 pCi/L Conduct a long-term test using an alpha track detector (3 months to 1 year). If confirmed, contact a licensed mitigator. Above 8 pCi/L Contact a licensed radon mitigator promptly.
Mitigation typically involves installing a depressurization system in the basement, crawl space, or under a slab-on-grade foundation — drawing radon out from beneath the home and venting it safely outside. Costs generally range from $500 to $2,500. A follow-up test after installation confirms the system is working effectively.
What about new construction?
If a home is being built, a builder can install a passive radon-reduction system during construction for roughly $350–$500. Once the home is complete, it should be tested. If levels are still elevated, a licensed mitigator can add a fan to the passive system to actively pull radon out from under the structure. Even with a mitigation system in place, the home should be retested every two years.
The bottom line
Every home — regardless of age, construction type, or location — has the potential for elevated radon. The only way to know your home's radon level is to test. Testing is simple, affordable, and can be done at any time of year. Given the health stakes, it's one of the most straightforward steps a homeowner, buyer, or seller can take.
For more information on licensed testers and mitigators in Illinois, visit the IEMA's radon resource site at radon.illinois.gov.
Practical radon checklist for Illinois homeowners
Use this step‑by‑step checklist to quickly assess your radon risk and plan testing and mitigation for your home.
1. Assess your home's risk factors
Location: Check if your county is listed as a moderate or high radon area on the IEMA or EPA radon zone maps.
Foundation type: Note whether you have a basement, crawl space, or slab‑on‑grade — all can have radon, but basements and crawl spaces tend to be higher risk.
Home age & condition: Look for visible cracks in floors or walls, gaps around pipes, or an uncovered sump pit.
Previous testing: Has your home ever been tested? If yes, note the date and result. If no, plan to test within the next 30 days.
💡 Pro Tip: Even if your neighbor's home tested low, your levels can be very different — always test your own home.
2. Prepare for a radon test
Choose your test type: short‑term kit, long‑term kit, or a licensed professional (recommended for real estate transactions).
Select the lowest livable level of your home (finished or unfinished basement, or first floor if no basement).
Before a short‑term test, close exterior doors and windows for at least 12 hours. Keep them closed as much as possible during the test.
Turn off whole‑house fans and avoid running fireplaces or wood stoves unless they are your primary heat source.
3. Place and run the test correctly
Set the detector 2–6 feet above the floor, away from exterior walls, drafts, windows, and direct sunlight.
Keep it out of kitchens, bathrooms, and laundry rooms where humidity can affect results.
Do not move the device or disturb the area while the test is running.
At the end of the test period, seal and mail the kit to the lab immediately (follow the kit instructions).
4. Interpret your results
Below 4 pCi/L: Record the result, keep your report, and plan to retest every 2 years or after major renovations.
4–8 pCi/L: Schedule a long‑term test (3–12 months) to confirm your average level, then consult a licensed mitigator if levels remain elevated.
Above 8 pCi/L: Contact a licensed Illinois radon mitigator promptly to discuss mitigation options and timelines.
📌 Key Takeaway: The EPA and CDC recommend fixing your home if the confirmed radon level is at or above 4 pCi/L.
5. Plan and complete mitigation (if needed)
Get at least two written estimates from licensed Illinois radon mitigators (search via radon.illinois.gov).
Review proposed system type (sub‑slab, drain‑tile, or crawl‑space depressurization) and warranty details. Typical system costs range from $500–$2,500.
Confirm that the contractor will install a visual indicator (such as a manometer) so you can easily see that the fan is operating.
After installation, perform a follow‑up radon test to verify that levels are reduced below 4 pCi/L. Keep this documentation with your home records.
6. Stay on top of radon over time
Retest your home every two years, or sooner if you finish a basement, add an addition, replace major HVAC equipment, or notice foundation changes.
If you have a mitigation system, glance at the fan indicator monthly to ensure it is running, and contact your mitigator if it appears off or abnormal.
When buying or selling a home, make radon testing and sharing of results part of your standard inspection process.
✅ Quick Action List: (1) Check when your home was last tested. (2) If it's been more than two years — or never — oschedule a licensed professional this week. (3) Put a reminder on your calendar to retest in two years.
