Radon levels in Knox County, Illinois
HighEPA Zone 1Predicted long-term basement average of 4.0 pCi/L (model estimate) across 16 ZIP codes - about 2.2× the US average of 1.8, about 2.1× the Illinois average of 1.9. Ranked #1 of 102 Illinois counties.
Test Knox County, IL now - and consider a continuous monitor
The model predicts a long-term basement average of 4.0 pCi/L here, at or above the EPA action level of 4. Homes in the same ZIP still vary widely, so a real test is the only way to know your number. A continuous digital monitor shows how your level swings with weather and season, which matters when you're near the action level.
Already tested at 4 pCi/L or higher? Find a certified mitigation professional (EPA). A mitigation system typically runs $800-$2,500 installed.
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Predicted (model estimate). The pCi/L figures on this page are long-term area averages from a peer-reviewed national model built on millions of real radon tests (2001-2021). They describe the typical home in this area - not your home, which can be several times higher or lower. The EPA radon zone is a separate, 1993 county-level classification. How the numbers work.
4.0 ± 0.06
pCi/L predicted basement mean (model SD)
2.4 ± 0.08
pCi/L predicted upstairs (above-ground) mean
2.9-4.3
range of ZIP-level basement predictions in the county
What this means for Knox
The typical home in Knox County is predicted to sit at or above the EPA action level of 4 pCi/L in the basement. In practice that means a large share of houses here would qualify for mitigation if tested, and buyers routinely ask for radon tests in Illinois transactions.
The 1993 EPA zone (1) and the 2001-2021 model agree for Knox. County figures weight each ZIP by its 2010 Census population, so they describe where people live rather than empty land.
Comparable Illinois counties: Warren County (4.0), Morgan County (3.6), Fulton County (3.6), Stark County (3.6).
ZIP codes in Knox County
Predicted basement and upstairs means by ZIP (model estimate). ZIPs whose land is mostly in this county.
| ZIP | Basement | Upstairs | Grade |
|---|---|---|---|
| 61401 | 4.3 ± 0.06 | 2.5 | High |
| 61410 | 3.4 ± 0.06 | 1.9 | Moderate |
| 61448 | 3.4 ± 0.05 | 2.2 | Moderate |
| 61488 | 3.5 ± 0.06 | 2.2 | Moderate |
| 61572 | 3.4 ± 0.06 | 2.0 | Moderate |
| 61467 | 3.7 ± 0.05 | 2.4 | Moderate |
| 61428 | 2.9 ± 0.05 | 1.8 | Moderate |
| 61436 | 3.5 ± 0.06 | 2.2 | Moderate |
| 61489 | 3.4 ± 0.06 | 2.1 | Moderate |
| 61414 | 3.6 ± 0.06 | 2.0 | Moderate |
| 61430 | 2.9 ± 0.05 | 1.8 | Moderate |
| 61458 | 3.3 ± 0.06 | 1.9 | Moderate |
| 61472 | 3.4 ± 0.06 | 2.2 | Moderate |
| 61485 | 3.2 ± 0.06 | 2.0 | Moderate |
| 61474 | 2.9 ± 0.05 | 1.8 | Moderate |
| 61439 | 2.9 ± 0.06 | 1.9 | Moderate |
If your test comes back at 4 pCi/L or higher
Mitigation is a routine job: a fan-driven pipe that vents soil gas from under the slab to above the roofline, typically $800-$2,500 installed (typical range; local quotes vary). Use certified professionals: EPA find-a-professional. Read the full mitigation guide.
Knox County radon questions
- Is radon high in Knox County, Illinois?
- High. The model predicts a long-term basement average of 4.0 pCi/L in Knox County (about 2.2× the US average of 1.8 and about 2.1× the Illinois average of 1.9). That is at or above the EPA action level of 4 pCi/L, so the typical home here would qualify for mitigation. Ranked 1 of 102 Illinois counties.
- Should I test for radon in Knox County?
- Yes, soon. With a predicted average of 4.0 pCi/L and at least one ZIP predicted at 4.3, many homes in Knox County will test above the 4 pCi/L action level. Use a short-term kit first; if it reads 2 or higher, confirm with a long-term test or continuous monitor before deciding on mitigation.
- What does EPA Radon Zone 1 mean for Knox County?
- Zone 1 - highest potential (predicted average > 4 pCi/L). The zone map dates from 1993 and classifies whole counties. The 2001-2021 model agrees with the zone here. Neither replaces a test of your own home.
- How much does radon mitigation cost in Knox County?
- A standard active sub-slab depressurization system typically runs $800-$2,500 installed nationally; Illinois quotes vary with foundation type (slab, crawlspace, basement), home size and local labor. Get two or three bids from certified mitigators listed by your state radon program or the EPA's find-a-professional page.
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