Is radon high in Joliet, Illinois?

Moderate. Averaging the model's ZIP-code predictions across Joliet (weighted by how much of the city each ZIP covers) gives a long-term basement mean of 2.4 pCi/L - about 1.3× the US average of 1.8 and about 1.3× the Illinois average of 1.9. That is in the 2-4 pCi/L range where the EPA says to consider fixing. Joliet ranks 7 of 34 Illinois cities on this site.

Which Joliet ZIP codes have the highest radon?

Predictions for the 8 modeled ZIP codes in Joliet range from 2.1 to 3.4 pCi/L in the basement. 0% of them are predicted at or above 4 pCi/L and 100% at or above 2. That spread is why the ZIP table below matters more than the city-wide number.

Should I test for radon in Joliet?

Yes, soon. With a predicted basement average of 2.4 pCi/L, a meaningful share of Joliet homes will test above the 4 pCi/L action level. Start with a short-term kit; if it reads 2 or higher, confirm with a long-term test or a continuous monitor before paying for mitigation.

What does EPA Radon Zone 2 mean for Joliet?

Joliet sits mainly in Will County, which the EPA classifies as Zone 2 - moderate potential (2-4 pCi/L). The zone map dates from 1993 and covers whole counties. The 2001-2021 model agrees with the zone for the city. Neither replaces a test of your own home.

Radon levels in Joliet, Illinois

ModerateEPA Zone 2

Predicted long-term basement average of 2.4 pCi/L (model estimate) across the 8 modeled ZIP codes in Joliet - about 1.3× the US average of 1.8, about 1.3× the Illinois average of 1.9. Ranked #7 of 34 Illinois cities on this site. Most of the city lies in Will County (its ZIPs also reach into 1 other county).

Test Joliet, IL - the EPA says "consider fixing" in this range

The predicted basement average here is 2.4 pCi/L, in the 2-4 pCi/L band where the EPA recommends considering mitigation. Plenty of individual homes in a moderate area test above 4. Start with a short-term test; if it comes back at 2 or higher, follow up with a long-term test or a continuous monitor.

Get a short-term test kit →Or track it with a continuous monitor

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.

2.4 ± 0.08

pCi/L predicted basement mean (model SD)

1.5 ± 0.10

pCi/L predicted upstairs (above-ground) mean

2.1-3.4

range of ZIP-level basement predictions in the city

of Joliet ZIPs predicted ≥ 4 pCi/L (100% ≥ 2)

What this means for Joliet

The typical Joliet home is predicted in the 2-4 pCi/L band. The EPA's guidance for this range is to consider fixing, because there is no known safe level and a meaningful minority of homes in a moderate area will test above 4.

The city figure is not a separate estimate: it is the mean of the model's ZIP-code predictions, weighted by the share of the city's land in each ZIP (Census 2020 ZCTA-to-place relationship file). The 1993 EPA zone (2) for Will and the 2001-2021 model agree here.

Comparable Illinois cities: Rockford (2.3), Plainfield (2.3), Bloomington (2.5), Elgin (2.2).

ZIP codes in Joliet

ZIPs that overlap the city, largest share of its land first. Predicted basement and upstairs means are model estimates; ZIPs the model does not cover show a dash.

ZIP	Share of city	Basement	Upstairs	Grade
60436	18%	2.1 ± 0.09	1.2	Moderate
60431	16%	2.2 ± 0.09	1.6	Moderate
60435	15%	2.4 ± 0.10	1.6	Moderate
60421	14%	2.6 ± 0.06	1.6	Moderate
60586	13%	2.3 ± 0.09	1.5	Moderate
60432	9%	2.2 ± 0.06	1.4	Moderate
60433	8%	2.3 ± 0.06	1.4	Moderate
60447	8%	3.4 ± 0.13	1.7	Moderate

Testing help in Illinois

Illinois's radon program page is at iemaohs.illinois.gov and, when we checked it, offered low-cost test kits. EPA state radon contacts page. If a test comes back at 4 pCi/L or higher, mitigation typically costs $800-$2,500 installed; use EPA find-a-professional and read the mitigation guide.

Joliet radon questions

Is radon high in Joliet, Illinois?: Moderate. Averaging the model's ZIP-code predictions across Joliet (weighted by how much of the city each ZIP covers) gives a long-term basement mean of 2.4 pCi/L - about 1.3× the US average of 1.8 and about 1.3× the Illinois average of 1.9. That is in the 2-4 pCi/L range where the EPA says to consider fixing. Joliet ranks 7 of 34 Illinois cities on this site.
Which Joliet ZIP codes have the highest radon?: Predictions for the 8 modeled ZIP codes in Joliet range from 2.1 to 3.4 pCi/L in the basement. 0% of them are predicted at or above 4 pCi/L and 100% at or above 2. That spread is why the ZIP table below matters more than the city-wide number.
Should I test for radon in Joliet?: Yes, soon. With a predicted basement average of 2.4 pCi/L, a meaningful share of Joliet homes will test above the 4 pCi/L action level. Start with a short-term kit; if it reads 2 or higher, confirm with a long-term test or a continuous monitor before paying for mitigation.
What does EPA Radon Zone 2 mean for Joliet?: Joliet sits mainly in Will County, which the EPA classifies as Zone 2 - moderate potential (2-4 pCi/L). The zone map dates from 1993 and covers whole counties. The 2001-2021 model agrees with the zone for the city. Neither replaces a test of your own home.

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