Is radon high in Chesterfield, Missouri?

Low. Averaging the model's ZIP-code predictions across Chesterfield (weighted by how much of the city each ZIP covers) gives a long-term basement mean of 1.9 pCi/L - close to the US average of 1.8 and close to the Missouri average of 2.2. That is below the EPA's 2 pCi/L "consider fixing" threshold, though individual homes still vary. Chesterfield ranks 13 of 15 Missouri cities on this site.

Which Chesterfield ZIP codes have the highest radon?

Predictions for the 3 modeled ZIP codes in Chesterfield range from 1.9 to 1.9 pCi/L in the basement. 0% of them are predicted at or above 4 pCi/L and 0% at or above 2. The city is fairly uniform, so the city-wide number is a reasonable guide for any neighborhood.

Should I test for radon in Chesterfield?

Yes, once. The EPA recommends testing every home regardless of area. A short-term kit costs little and settles the question for your house; Chesterfield's low predicted average describes the typical home, not yours.

What does EPA Radon Zone 2 mean for Chesterfield?

Chesterfield sits mainly in St. Louis 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 newer model's city average of 1.9 pCi/L does not line up with Zone 2, which is common - the EPA itself says high-radon homes exist in every zone. Neither replaces a test of your own home.

Radon levels in Chesterfield, Missouri

LowEPA Zone 2

Predicted long-term basement average of 1.9 pCi/L (model estimate) across the 3 modeled ZIP codes in Chesterfield - close to the US average of 1.8, close to the Missouri average of 2.2. Ranked #13 of 15 Missouri cities on this site. Most of the city lies in St. Louis County.

Test Chesterfield, MO once anyway - radon varies house to house

The predicted basement average here is 1.9 pCi/L, below the EPA's 2 pCi/L "consider fixing" threshold. That's good news for the area - but the EPA still recommends every home be tested, because foundation cracks, soil pockets and ventilation make one house very different from its neighbor. One inexpensive kit settles it.

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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.

1.9 ± 0.07

pCi/L predicted basement mean (model SD)

1.2 ± 0.07

pCi/L predicted upstairs (above-ground) mean

1.9-1.9

range of ZIP-level basement predictions in the city

of Chesterfield ZIPs predicted ≥ 4 pCi/L (0% ≥ 2)

What this means for Chesterfield

The typical Chesterfield home is predicted below 2 pCi/L, the lowest band. That describes the average house; the ZIP-level predictions inside the city still span 1.9 to 1.9 pCi/L.

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). Note that the EPA classifies St. Louis County as Zone 2 while the newer model predicts 1.9 pCi/L for Chesterfield; where they disagree, we grade on the model but show both.

Comparable Missouri cities: Columbia (1.9), Florissant (1.8), O'Fallon (1.9), Wentzville (2.0).

ZIP codes in Chesterfield

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
63017	50%	1.9 ± 0.06	1.3	Low
63005	47%	1.9 ± 0.08	1.1	Low
63141	2%	1.9 ± 0.07	1.2	Low

Testing help in Missouri

Missouri's radon program page is at health.mo.gov and, when we checked it, offered free radon test kits for Missouri residents. 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.

Chesterfield radon questions

Is radon high in Chesterfield, Missouri?: Low. Averaging the model's ZIP-code predictions across Chesterfield (weighted by how much of the city each ZIP covers) gives a long-term basement mean of 1.9 pCi/L - close to the US average of 1.8 and close to the Missouri average of 2.2. That is below the EPA's 2 pCi/L "consider fixing" threshold, though individual homes still vary. Chesterfield ranks 13 of 15 Missouri cities on this site.
Which Chesterfield ZIP codes have the highest radon?: Predictions for the 3 modeled ZIP codes in Chesterfield range from 1.9 to 1.9 pCi/L in the basement. 0% of them are predicted at or above 4 pCi/L and 0% at or above 2. The city is fairly uniform, so the city-wide number is a reasonable guide for any neighborhood.
Should I test for radon in Chesterfield?: Yes, once. The EPA recommends testing every home regardless of area. A short-term kit costs little and settles the question for your house; Chesterfield's low predicted average describes the typical home, not yours.
What does EPA Radon Zone 2 mean for Chesterfield?: Chesterfield sits mainly in St. Louis 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 newer model's city average of 1.9 pCi/L does not line up with Zone 2, which is common - the EPA itself says high-radon homes exist in every zone. Neither replaces a test of your own home.

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