Long-term kit
RL416 long-term radon test kit, lab fee included
- Lab fee included
Method: Alpha track
In home: 90 days to 12 months
Locations and reports
Radon Levels in Marshall County, Indiana
EPA puts Marshall County in Zone 1, its highest radon zone, and 39.7% of its 383 reported radon tests (2008 to 2017, laboratory totals) were at or above 4 pCi/L. Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Share at 4+ pCi/L
39.7%
0.8 pts above IN
- Marshall
- 39.7%
- Indiana
- 38.9%
383 tests, 2008 to 2017
Median result
3.2pCi/L
Below action level
- Marshall
- 3.2 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
383
20th of 69 by tests
- Marshall
- 383
- St. Joseph
- 7,346
Reported to CDC before any fix, 2008 to 2017
EPA radon zone
Zone 1
Highest potential
- Zone 1
- 2
- 3
1 highest, 3 lowest
EPA predicts over 4 pCi/L indoors
Rank in Indiana
44 of 69
Middle half
- Marshall
- 39.7%
- Miami
- 63.3%
By share, of 69 with 30+ tests
Read a result for Marshall County
Starts at Marshall County's median, 3.2 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 3.2 pCi/L
Between 2 and 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is between 2 and 4 pCi/L. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. Marshall County's median reported result, 2008 to 2017.
The data
Marshall County, At a glance
Marshall County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Marshall County in
USGS geologic potential: High across 88% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Marshall County, 2008 to 2017, laboratory
Under 2 pCi/L: 30%2 to 4 pCi/L: 30%4 pCi/L and above: 40%
Of 383 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 114 | 29.8% |
| 2 to 4 pCi/L | 117 | 30.5% |
| 4 pCi/L and above | 152 | 39.7% |
What these figures count
These are the 383 tests reported to CDC for Marshall County over 2008 to 2017 (laboratory totals), many from homes being sold or already suspected of a problem: they describe the county's reported tests, not this house.
Measured: CDC tracking data. Figure above: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).
Marshall County, Compared
Marshall County radon figures, compared
Calculated by Radon411In Marshall County, about 4 in 10 reported tests over the 2008 to 2017 laboratory totals (152 of 383) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 4.0 points higher. Across 92 Indiana counties pooled together, 38.9% of tests reached that level, so Marshall County runs 0.8 points above its state.
Of 4 neighbours with a figure, 3 reported a larger share at or above 4 pCi/L and 1 a smaller one; the spread is 29.3% (St. Joseph County) to 50.6% (Kosciusko County). By share, Marshall County is 44th of 69 Indiana counties with 30 or more tests for the same period.
Half the tests came in under 3.2 pCi/L and half over it; the single highest reached 73.1 pCi/L. Below the action level, 114 tests (29.8%) came in under 2 pCi/L, against 32.8% statewide, and 117 tests (30.5%) fell between 2 and 4, against 28.3% statewide.
Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 39.7% share point the same way here. USGS geology rates 88% of the county's land high radon potential. CDC also counts 20 tests taken after mitigation in Marshall County for the same period: tests in homes where a fix was already in.
CDC's ten-year totals for Marshall County went from 248 tests (2005 to 2014) to 383 (2008 to 2017), the share going from 41.1% to 39.7%.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Marshall County, Geology
The ground under Marshall County
PredictedMost of the ground under Marshall County is one class on USGS's geologic map: 87.7% of its land is high radon potential, with 12.3% moderate. The map puts 87.7% of Marshall County in the area it calls Saginaw Lobe and 12.3% in Kankakee Outwash and Lacustrine Plain. USGS gives the first a radon index of 12, in the high band (12 to 17), and the second 10, in the moderate band (9 to 11).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Saginaw Lobe | Clayey and loamy glacial deposits. | High | 12 | 87.7% |
| Kankakee Outwash and Lacustrine Plain | Moraine deposits, outwash and dune sands. | Moderate | 10 | 12.3% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Marshall County beside the ground around it
Marshall County has more high-potential ground than Indiana as a whole: 87.7% of its land against 56.6%. Of the 6 counties that border it, 3 have more high-potential ground, Elkhart County the most at 100%.
The map rates the ground, not the air in any home.
Local help
Marshall County, Local resources
Radon testing and mitigation in Marshall County
- Indiana's radon programIndiana Department of HealthIndiana's radon program licenses or certifies radon professionals and offers free or discounted test kits, and answers questions about testing and mitigation in Indiana.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
To purchase a low-cost radon short term or long term test kit, please visit the American Lung Association
- Compare kits
- Professionals in Indiana17 professionals are listed in Indiana.
What Indiana's program says
- Phone
- 1-800-272-9723
- Licensing of radon professionals
According to the Indiana Radon Rule, 410 IAC 5.1, everyone who is serving Indiana by doing radon testing, analysis and mitigation (radon reduction) in residential structures must be certified by the Indiana State Department of Health.
What it means
Marshall County, Questions
Questions about radon in Marshall County
Are radon levels high in Marshall County?
Over the 2008 to 2017 laboratory totals, 39.7% of the radon tests reported to CDC for Marshall County, Indiana were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.2 pCi/L. Of 69 Indiana counties with 30 or more tests for the same period, 43 reported a higher share; pooled, the state comes to 38.9%.
Which counties border Marshall County?
Marshall County borders 6 counties: Fulton County, Starke County, St. Joseph County, Kosciusko County, Pulaski County and Elkhart County.
Products
Marshall County, Products
Testing a home in Marshall County
In Marshall County, 39.7% of 383 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 38.9% pooled across Indiana. In Zone 1 the year-round level in Marshall County is the one to know: a long-term test (more than 90 days) or a monitor, with a short-term kit for a first answer.
Test kits and monitors3
See every kit and monitor
Monitor
View Radon Wi-Fi radon monitor with an e-paper display
- C-NRPP 2024/25: Approved
- Battery
- Wi-Fi, Bluetooth
- Screen, app
Method: Alpha spectrometry
Readings: Every 60 minutes
Short-term kit
Radon Short Term Test Kit short-term charcoal radon test kit, lab fee included
- Lab fee included
Method: Charcoal
In home: 2 to 7 days
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Marshall County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Marshall County
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Marshall County, Bordering counties
Counties bordering Marshall County
Calculated by Radon411- Radon levels in Kosciusko CountyEPA zone 1
50.6%at or above 4 pCi/L
Median 4.0 pCi/L · 1,248 tests · 10.9 points above Marshall County
- Radon levels in Fulton CountyEPA zone 1
46.4%at or above 4 pCi/L
Median 3.3 pCi/L · 97 tests · 6.7 points above Marshall County
- Radon levels in Elkhart CountyEPA zone 1
46.4%at or above 4 pCi/L
Median 3.7 pCi/L · 2,856 tests · 6.7 points above Marshall County
- Radon levels in Pulaski CountyEPA zone 2
31.8%at or above 4 pCi/L
Median 2.3 pCi/L · 22 tests · 7.9 points below Marshall County
- Radon levels in St. Joseph CountyEPA zone 1
29.3%at or above 4 pCi/L
Median 2.7 pCi/L · 7,346 tests · 10.4 points below Marshall County
- Radon levels in Starke CountyEPA zone 2
4.2%at or above 4 pCi/L
Median 1.6 pCi/L · 24 tests · 35.5 points below Marshall County
Marshall County, Cities and towns
Cities and towns in Marshall County
The Census Bureau estimates 46,599 residents in Marshall County for July 1, 2025, 535 more than in 2020 (+1.2%). That works out to 105 people per square mile of land. Its largest town, Plymouth, has 11,081 residents, 23.8% of the total. Together its 6 incorporated places hold 44.7% of those residents; the other 55.3% live outside any of them. CDC's 383 reported tests for 2008 to 2017 work out to 8.2 per 1,000 residents (2025 estimate), close to Indiana's 6.2.
From Plymouth to La Paz, CDC publishes no figure by town: each reads Marshall County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Plymouth | 11,081 | +8.6% | 23.8% |
| Bremen | 4,592 | −1.9% | 9.9% |
| Argos | 1,761 | −0.8% | 3.8% |
| Bourbon | 1,674 | −1.4% | 3.6% |
| Culver | 1,256 | +10.8% | 2.7% |
| La Paz | 467 | −1.1% | 1.0% |
6 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025).
Marshall County, Homes
Homes in Marshall County
Marshall County is a place of houses on their own lots: 81% of its 19,959 homes are detached single-family houses, against 73% across Indiana. Half of its homes were built before 1973, close to Indiana's 1976: 37% date from before 1960 and 17% from 2000 or later. Owners live in 77% of the occupied homes (Indiana: 70%), so for most households a test and a fix are their own to order.
| Homes | Marshall County | Indiana |
|---|---|---|
| Housing units | 19,959 | 2,953,344 |
| Detached houses | 81% | 73% |
| In buildings of 5 or more | 6% | 13% |
| Mobile homes | 7% | 4% |
| Built before 1960 | 37% | 32% |
| Built since 2000 | 17% | 21% |
| Middle year built | 1973 | 1976 |
| Owner-occupied | 77% | 70% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.