Is radon high in Delaware, Ohio?

High. Averaging the model's ZIP-code predictions across Delaware (weighted by how much of the city each ZIP covers) gives a long-term basement mean of 4.9 pCi/L - about 2.7× the US average of 1.8 and about 1.7× the Ohio average of 2.8. That is at or above the EPA action level of 4 pCi/L. Delaware ranks 2 of 27 Ohio cities on this site.

Which Delaware ZIP codes have the highest radon?

Predictions for the 2 modeled ZIP codes in Delaware range from 3.6 to 4.9 pCi/L in the basement. 50% 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 Delaware?

Yes, soon. With a predicted basement average of 4.9 pCi/L and ZIPs predicted as high as 4.9, a meaningful share of Delaware 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 Delaware?

Delaware sits mainly in Delaware 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 2001-2021 model agrees with the zone for the city. Neither replaces a test of your own home.

Radon levels in Delaware, Ohio

HighEPA Zone 1

Predicted long-term basement average of 4.9 pCi/L (model estimate) across the 2 modeled ZIP codes in Delaware - about 2.7× the US average of 1.8, about 1.7× the Ohio average of 2.8. Ranked #2 of 27 Ohio cities on this site. Most of the city lies in Delaware County.

Test Delaware, OH now - and consider a continuous monitor

The model predicts a long-term basement average of 4.9 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.

Get a continuous radon monitor →Or start with a short-term test kit

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.

4.9 ± 0.08

pCi/L predicted basement mean (model SD)

2.7 ± 0.07

pCi/L predicted upstairs (above-ground) mean

3.6-4.9

range of ZIP-level basement predictions in the city

50%

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

What this means for Delaware

The typical home in Delaware is predicted to sit at or above the EPA action level of 4 pCi/L in the basement. A large share of houses here would qualify for mitigation if tested, and buyers routinely ask for radon tests in Ohio transactions.

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 (1) for Delaware and the 2001-2021 model agree here.

Comparable Ohio cities: Columbus (4.3), Dublin (4.2), Mansfield (3.9), Springfield (3.6).

ZIP codes in Delaware

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
43015	98%	4.9 ± 0.08	2.7	High
43035	2%	3.6 ± 0.07	2.3	Moderate

Testing help in Ohio

Ohio's radon program page is at odh.ohio.gov; it lists testing and certified-mitigator guidance. 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.

Delaware radon questions

Is radon high in Delaware, Ohio?: High. Averaging the model's ZIP-code predictions across Delaware (weighted by how much of the city each ZIP covers) gives a long-term basement mean of 4.9 pCi/L - about 2.7× the US average of 1.8 and about 1.7× the Ohio average of 2.8. That is at or above the EPA action level of 4 pCi/L. Delaware ranks 2 of 27 Ohio cities on this site.
Which Delaware ZIP codes have the highest radon?: Predictions for the 2 modeled ZIP codes in Delaware range from 3.6 to 4.9 pCi/L in the basement. 50% 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 Delaware?: Yes, soon. With a predicted basement average of 4.9 pCi/L and ZIPs predicted as high as 4.9, a meaningful share of Delaware 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 Delaware?: Delaware sits mainly in Delaware 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 2001-2021 model agrees with the zone for the city. Neither replaces a test of your own home.

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