The short version
Joliet is a Will County city southwest of Chicago. Across 3,317 radon tests recorded in Joliet ZIP codes, the average result was about 5.8 pCi/L—well above the EPA's 4 pCi/L action level, and higher than the Illinois state average.4 Testing your own home is the only way to know its level.
Fastest reliable path: put a continuous monitor in your lowest lived-in level for at least a week. Our top pick is the RadonEye RD200, or see the full best radon detectors guide.
Radon risk in Joliet and Illinois
Joliet radon at a glance
5.8
avg pCi/L
3,317
tests recorded
261.9
highest pCi/L
Average of recorded radon tests in Joliet ZIP codes (60431, 60432, 60433, 60435, 60436), IEMA measurement data.4
A local average of 5.8 pCi/L is well above the EPA action level—meaning a majority of the Joliet homes in this dataset tested high, and at least one reading reached a striking 261.9 pCi/L. Joliet also sits inside a high-radon state. According to the American Lung Association, citing IEMA:1
- 5.1The average indoor radon level in Illinois is 5.1 pCi/L—above the EPA's 4 pCi/L action level.
- ~45%About one in two homes tested in Illinois (roughly 45%) are at or above 4 pCi/L.
- 1,160As many as 1,160 Illinois residents per year are at risk of radon-related lung cancer.
The EPA maps every U.S. county into radon Zones 1–3, but stresses that elevated radon turns up in all three zones and that every home should be tested regardless of its zone.2
What counts as a high radon level?
The EPA recommends fixing your home at 4 pCi/L or higher, and considering a fix between 2 and 4 pCi/L.2 Given Joliet's local average sits above 4, a test here has a real chance of coming back in mitigation territory—in which case the next step is mitigation.
How to test your Joliet home
Continuous monitor (recommended)
Reusable, shows levels day to day, and confirms a fix later. The RadonEye RD200 is our accuracy-per-dollar pick; the Airthings Wave Plus adds air-quality sensors.
Buy RadonEye RD200 →Charcoal test kit (cheapest)
An EPA-approved short-term kit is the cheapest way to get a first number; you mail it to a lab. See our radon test kit picks.
How to test for radon →Place the device in your lowest lived-in level, 20"+ off the floor and away from drafts, and let it run at least seven days. Not sure home monitors can be trusted? See are radon detectors accurate?
Buying or selling in Joliet? Know the Illinois rules
Under the Illinois Radon Awareness Act, sellers of residential property must give buyers a radon disclosure form and the IEMA radon pamphlet, and disclose any known radon records, before a sale.3 Illinois also requires radon measurement and mitigation to be performed by IEMA-licensed professionals.3
If you need to reduce levels, a typical system runs several hundred to a few thousand dollars—see our radon mitigation cost guide, or the best radon fans if you're a confident DIYer.
Test your Joliet home
With a local average above the action level, testing is the smart first move.
See the Best Radon Detectors →Frequently Asked Questions
Does Joliet have a radon problem?
Local data suggests yes, notably so. Across 3,317 radon tests recorded in Joliet ZIP codes in IEMA's measurement data, the average was about 5.8 pCi/L—well above the EPA action level—with readings as high as 261.9 pCi/L.4 Statewide, IEMA data (via the American Lung Association) puts the average at 5.1 pCi/L with about one in two tested homes at or above 4 pCi/L.1 Radon still varies house to house, so test your own home.
What radon level is dangerous?
The EPA recommends fixing at 4 pCi/L or higher and considering a fix between 2 and 4.2 There is no completely safe level, so lower is better.
Do I still need to test if my neighbor's level is low?
Yes—levels differ significantly between neighboring homes due to foundation, construction, and soil. The EPA recommends testing every home individually.2
Is radon disclosure required when selling in Illinois?
Yes. The Illinois Radon Awareness Act requires sellers to give buyers a radon disclosure form and pamphlet and disclose known radon records before a sale.3
What's the best radon detector for a Joliet home?
For continuous monitoring, the RadonEye RD200 is our accuracy-per-dollar pick; the Airthings Wave Plus adds air-quality sensors. See the full best radon detectors guide.
Sources
- American Lung Association, Radon in Illinois (statistics attributed to Illinois IEMA): state average 5.1 pCi/L, ~45% of tested homes at/above 4 pCi/L, up to 1,160 residents/year at risk.
- U.S. EPA, EPA Map of Radon Zones: 4 pCi/L action level; consider fixing 2–4 pCi/L; test every home regardless of zone.
- Illinois Emergency Management Agency (IEMA), Radon Program: Illinois Radon Awareness Act disclosure requirements and radon professional licensing.
- Illinois Emergency Management Agency (IEMA), Interactive Radon Map (measurement records from licensed professionals, highest result per address). Query of Joliet ZIP codes 60431, 60432, 60433, 60435, 60436: 3,317 tests, average 5.8 pCi/L, maximum 261.9 pCi/L.