Radon levels in Marshall County, Minnesota
ModerateEPA Zone 1Predicted long-term basement average of 3.3 pCi/L (model estimate) across 9 ZIP codes - about 1.8× the US average of 1.8, about 1.3× the Minnesota average of 2.4. Ranked #35 of 87 Minnesota counties.
Test Marshall County, MN - the EPA says "consider fixing" in this range
The predicted basement average here is 3.3 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.
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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.
3.3 ± 0.06
pCi/L predicted basement mean (model SD)
1.9 ± 0.08
pCi/L predicted upstairs (above-ground) mean
2.1-3.7
range of ZIP-level basement predictions in the county
Measured radon tests in Marshall County (Minnesota Department of Health (MN Public Health Data Access), 2016-2025)
Actual results from home radon tests reported to the state, separate from the model estimate above. Coverage: 2016-2025.
- Measured mean
- 5.9 pCi/L
- Measured median
- 3.8 pCi/L
- Results ≥ 4 pCi/L
- 46.3%
- Results ≥ 2 pCi/L
- 76.4%
- Sample
- about 12 properties tested per year
| Figure | Model (predicted) | State tests (measured) |
|---|---|---|
| Mean, pCi/L | 3.3 basement | 5.9 |
| Share ≥ 4 pCi/L | not a model output | 46.3% |
The measured mean runs 2.7 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: Minnesota radon test results by county, Minnesota Department of Health (MN Public Health Data Access). Minnesota public data (Minn. Stat. ch. 13). Method and download.
Tested above 4 pCi/L? Get a mitigation quote from a certified local contractor
Typical mitigation runs $800-$2,500 and takes a day. Installers guarantee the system brings levels under 4 pCi/L. Tell us where you are in Marshall County, MN and a certified mitigator will follow up - no obligation.
What this means for Marshall
The typical Marshall County 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 roughly one home in several in a moderate area will test above 4.
Note that the EPA classifies Marshall County as Zone 1 while the newer model predicts 3.3 pCi/L. The zone map predates two decades of test data; where they disagree, we grade on the model but show both. County figures weight each ZIP by its 2010 Census population, so they describe where people live rather than empty land.
Comparable Minnesota counties: Norman County (3.3), McLeod County (3.2), Goodhue County (3.2), Winona County (3.2). The state's highest is Rock County at 4.7 pCi/L.
ZIP codes in Marshall County
Predicted basement and upstairs means by ZIP (model estimate). ZIPs whose land is mostly in this county.
If your test comes back at 4 pCi/L or higher
Mitigation is a routine job: a fan-driven pipe that vents soil gas from under the slab to above the roofline, typically $800-$2,500 installed (typical range; local quotes vary). Use certified professionals: EPA find-a-professional. Read the full mitigation guide.
Marshall County radon questions
- Is radon high in Marshall County, Minnesota?
- Moderate. The model predicts a long-term basement average of 3.3 pCi/L in Marshall County (about 1.8× the US average of 1.8 and about 1.3× the Minnesota average of 2.4). That is in the 2-4 pCi/L range where the EPA recommends considering mitigation. Ranked 35 of 87 Minnesota counties.
- What do actual radon tests show in Marshall County?
- Minnesota Department of Health (MN Public Health Data Access) data covering 2016-2025 (about 12 properties tested per year) shows an average of 5.9 pCi/L, a median of 3.8, 46.3% of results at or above the 4 pCi/L action level, 76.4% at or above 2. These are voluntary home tests, so they skew toward basements and toward homes where radon was suspected; the model's predicted long-term basement average for the county is 3.3 pCi/L.
- Should I test for radon in Marshall County?
- Yes, soon. With a predicted average of 3.3 pCi/L, many homes in Marshall County will test above the 4 pCi/L action level. Use a short-term kit first; if it reads 2 or higher, confirm with a long-term test or continuous monitor before deciding on mitigation.
- What does EPA Radon Zone 1 mean for Marshall County?
- Zone 1 - highest potential (predicted average > 4 pCi/L). The zone map dates from 1993 and classifies whole counties. The newer model's predicted average of 3.3 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.
- How much does radon mitigation cost in Marshall County?
- A standard active sub-slab depressurization system typically runs $800-$2,500 installed nationally; Minnesota quotes vary with foundation type (slab, crawlspace, basement), home size and local labor. Get two or three bids from certified mitigators listed by your state radon program or the EPA's find-a-professional page.
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