The short version
Naperville is a western Chicago suburb in DuPage and Will counties. Across 32,606 radon tests recorded in Naperville ZIP codes, the average result was about 4.1 pCi/L—right at the EPA's 4 pCi/L action level.4 You still can't know your own home's level without testing it, and testing is inexpensive.
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 Naperville and Illinois
Naperville radon at a glance
4.1
avg pCi/L
32,606
tests recorded
116.6
highest pCi/L
Average of recorded radon tests in Naperville ZIP codes (60540, 60563, 60564, 60565), IEMA measurement data.4
That local average lands right at the EPA action level—which means a large share of Naperville homes test above it. And Naperville 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 A county or neighbor's number can't tell you your home's level.
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 There is no completely safe level, so lower is always better. If a Naperville test comes back at or above 4, the next step is mitigation.
How to test your Naperville home
Two good options, depending on whether you want a quick snapshot or ongoing awareness:
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 Naperville? 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 Naperville home
Start with an accurate continuous monitor, then act on the number.
See the Best Radon Detectors →Frequently Asked Questions
Does Naperville have a radon problem?
Local data suggests yes. Across 32,606 radon tests recorded in Naperville ZIP codes in IEMA's measurement data, the average result was about 4.1 pCi/L—right at the EPA action level—with readings as high as 116.6 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 Naperville 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 and Illinois radon zones (PDF): 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 Naperville ZIP codes 60540, 60563, 60564, 60565: 32,606 tests, average 4.1 pCi/L, maximum 116.6 pCi/L.