Radon levels in Harrisburg, Pennsylvania
ModerateEPA Zone 1Predicted long-term basement average of 2.6 pCi/L (model estimate) across the 6 modeled ZIP codes in Harrisburg - about 1.4× the US average of 1.8, close to the Pennsylvania average of 2.3. Ranked #3 of 12 Pennsylvania cities on this site. Most of the city lies in Dauphin County.
Test Harrisburg, PA - the EPA says "consider fixing" in this range
The predicted basement average here is 2.6 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.
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. Measured state test results are shown separately below, labeled with their source and years. How the numbers work.
2.6 ± 0.08
pCi/L predicted basement mean (model SD)
1.6 ± 0.09
pCi/L predicted upstairs (above-ground) mean
2.1-4.2
range of ZIP-level basement predictions in the city
17%
of Harrisburg ZIPs predicted ≥ 4 pCi/L (100% ≥ 2)
Measured radon tests in Dauphin County (Pennsylvania Department of Environmental Protection, 1988-2025)
Actual results from home radon tests reported to the state, separate from the model estimate above. Coverage: 1988-2026.
- Measured mean
- 9.9 pCi/L
- Measured median
- 4.3 pCi/L
- Results ≥ 4 pCi/L
- 52.2%
- Results ≥ 2 pCi/L
- 72.4%
- Basement tests, mean
- 11.0 pCi/L
- Sample
- 25,981 tests
| Figure | Model (predicted) | State tests (measured) |
|---|---|---|
| Mean, pCi/L | 3.4 basement | 9.9 (11.0 basement) |
| Share ≥ 4 pCi/L | not a model output | 52.2% |
The measured mean runs 6.6 pCi/L above the model because state test data is voluntary and skews toward basements, winter, and homeowners who already suspected a problem, while the model estimates the long-term average across all homes.
Source: Radon Test Results September 1986 - Current Annual County Environmental Protection, Pennsylvania Department of Environmental Protection, Bureau of Radiation Protection. Public Domain (as stated on data.pa.gov). Method and download.
What this means for Harrisburg
The typical Harrisburg 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 Dauphin County as Zone 1 while the newer model predicts 2.6 pCi/L for Harrisburg; where they disagree, we grade on the model but show both.
Comparable Pennsylvania cities: Lancaster (2.8), Bethlehem (2.4), Reading (2.3), Allentown (2.3).
ZIP codes in Harrisburg
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.
Testing help in Pennsylvania
Pennsylvania's radon program page is at www.pa.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.
Harrisburg radon questions
- Is radon high in Harrisburg, Pennsylvania?
- Moderate. Averaging the model's ZIP-code predictions across Harrisburg (weighted by how much of the city each ZIP covers) gives a long-term basement mean of 2.6 pCi/L - about 1.4× the US average of 1.8 and close to the Pennsylvania average of 2.3. That is in the 2-4 pCi/L range where the EPA says to consider fixing. Harrisburg ranks 3 of 12 Pennsylvania cities on this site.
- What do actual radon tests show around Harrisburg?
- Pennsylvania Department of Environmental Protection publishes results for Dauphin County (not the city alone) covering 1988-2025 (25,981 tests): an average of 9.9 pCi/L, a median of 4.3, 52.2% of results at or above the 4 pCi/L action level. These are voluntary home tests, so they skew toward basements and toward homes where radon was suspected; the model's predicted basement average for Harrisburg is 2.6 pCi/L.
- Which Harrisburg ZIP codes have the highest radon?
- Predictions for the 6 modeled ZIP codes in Harrisburg range from 2.1 to 4.2 pCi/L in the basement. 17% 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 Harrisburg?
- Yes, soon. With a predicted basement average of 2.6 pCi/L and ZIPs predicted as high as 4.2, a meaningful share of Harrisburg 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 Harrisburg?
- Harrisburg sits mainly in Dauphin 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 2.6 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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