Is radon high in Casper, Wyoming?

Moderate. Averaging the model's ZIP-code predictions across Casper (weighted by how much of the city each ZIP covers) gives a long-term basement mean of 3.2 pCi/L - about 1.7× the US average of 1.8 and close to the Wyoming average of 3.0. That is in the 2-4 pCi/L range where the EPA says to consider fixing. Casper ranks 1 of 2 Wyoming cities on this site.

Which Casper ZIP codes have the highest radon?

Predictions for the 3 modeled ZIP codes in Casper range from 3.0 to 3.6 pCi/L in the basement. 0% of them are predicted at or above 4 pCi/L and 100% 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 Casper?

Yes, soon. With a predicted basement average of 3.2 pCi/L, a meaningful share of Casper 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 1 mean for Casper?

Casper sits mainly in Natrona County, which the EPA classifies as Zone 1 - highest potential (predicted average > 4 pCi/L). The zone map dates from 1993 and covers whole counties. The newer model's city average of 3.2 pCi/L does not line up with Zone 1, 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 Casper, Wyoming

ModerateEPA Zone 1

Predicted long-term basement average of 3.2 pCi/L (model estimate) across the 3 modeled ZIP codes in Casper - about 1.7× the US average of 1.8, close to the Wyoming average of 3.0. Ranked #1 of 2 Wyoming cities on this site. Most of the city lies in Natrona County.

Test Casper, WY - the EPA says "consider fixing" in this range

The predicted basement average here is 3.2 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.

3.2 ± 0.07

pCi/L predicted basement mean (model SD)

2.1 ± 0.08

pCi/L predicted upstairs (above-ground) mean

3.0-3.6

range of ZIP-level basement predictions in the city

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

What this means for Casper

The typical Casper 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). Note that the EPA classifies Natrona County as Zone 1 while the newer model predicts 3.2 pCi/L for Casper; where they disagree, we grade on the model but show both.

Comparable Wyoming cities: Cheyenne (2.4), Boise (2.4), Meridian (2.0), Nampa (1.9).

ZIP codes in Casper

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
82601	50%	3.1 ± 0.06	2.0	Moderate
82604	27%	2.9 ± 0.06	2.5	Moderate
82609	22%	3.6 ± 0.10	2.1	Moderate

Testing help in Wyoming

We link only state program pages we could verify, and Wyoming's did not respond when we checked, so start from the 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.

Casper radon questions

Is radon high in Casper, Wyoming?: Moderate. Averaging the model's ZIP-code predictions across Casper (weighted by how much of the city each ZIP covers) gives a long-term basement mean of 3.2 pCi/L - about 1.7× the US average of 1.8 and close to the Wyoming average of 3.0. That is in the 2-4 pCi/L range where the EPA says to consider fixing. Casper ranks 1 of 2 Wyoming cities on this site.
Which Casper ZIP codes have the highest radon?: Predictions for the 3 modeled ZIP codes in Casper range from 3.0 to 3.6 pCi/L in the basement. 0% of them are predicted at or above 4 pCi/L and 100% 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 Casper?: Yes, soon. With a predicted basement average of 3.2 pCi/L, a meaningful share of Casper 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 1 mean for Casper?: Casper sits mainly in Natrona County, which the EPA classifies as Zone 1 - highest potential (predicted average > 4 pCi/L). The zone map dates from 1993 and covers whole counties. The newer model's city average of 3.2 pCi/L does not line up with Zone 1, 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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