Long-term kit
RL116 long-term radon test kit
- Lab fee extra
Method: Alpha track
In home: 90 days to 12 months
Locations and reports
Radon Levels in Hardin County, Ohio
EPA puts Hardin County in Zone 1, its highest radon zone, and high results are common there: 43.3% of the 67 radon tests reported to CDC (2008 to 2017, laboratory totals) came back 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
43.3%
9.0 pts below OH
- Hardin
- 43.3%
- Ohio
- 52.3%
67 tests, 2008 to 2017
Median result
3.4pCi/L
Below action level
- Hardin
- 3.4 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
67
70th of 79 by tests
- Hardin
- 67
- Franklin
- 16,142
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 Ohio
62 of 79
Lowest quarter
- Hardin
- 43.3%
- Pickaway
- 81.4%
By share, of 79 with 30+ tests
Read a result for Hardin County
Starts at Hardin County's median, 3.4 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 3.4 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. Hardin County's median reported result, 2008 to 2017.
The data
Hardin County, At a glance
Hardin County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Hardin County in
USGS geologic potential: High across 100% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Hardin County, 2008 to 2017, laboratory
Under 2 pCi/L: 31%2 to 4 pCi/L: 26%4 pCi/L and above: 43%
Of 67 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 21 | 31.3% |
| 2 to 4 pCi/L | 17 | 25.4% |
| 4 pCi/L and above | 29 | 43.3% |
What these figures count
These are the 67 tests reported to CDC for Hardin 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).
Hardin County, Compared
Hardin County radon figures, compared
Calculated by Radon411In Hardin County, about 4 in 10 reported tests over the 2008 to 2017 laboratory totals (29 of 67) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 7.6 points higher. Across 88 Ohio counties pooled together, 52.3% of tests reached that level, so Hardin County runs 9.0 points below its state.
Of 7 neighbours with a figure, all 7 reported a larger share at or above 4 pCi/L; the spread is 46.2% (Hancock County) to 73.6% (Logan County). By share, Hardin County is 62nd of 79 Ohio counties with 30 or more tests for the same period.
Half the tests came in under 3.4 pCi/L and half over it; the single highest reached 21.8 pCi/L. Below the action level, 21 tests (31.3%) came in under 2 pCi/L, against 23.1% statewide, and 17 tests (25.4%) fell between 2 and 4, against 24.6% statewide.
Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 43.3% share point the same way here. USGS geology rates 100% of the county's land high radon potential.
CDC's ten-year totals for Hardin County went from 54 tests (2005 to 2014) to 67 (2008 to 2017), the share going from 38.9% to 43.3%.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Hardin County, Geology
The ground under Hardin County
PredictedUSGS's geologic map puts all of Hardin County's mapped land in one class: high radon potential. All of it lies in the area the map calls Till Plains, to which USGS gives a radon index of 14, in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Till Plains | Glacial deposits underlain by Ordovician through Devonian limestone and shale. | High | 14 | 100% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Hardin County beside the ground around it
Hardin County has more high-potential ground than Ohio as a whole: 100% of its land against 62.8%. Of the 7 counties that border it, none has as large a share of high-potential ground; Allen County comes nearest at 100%.
The map rates the ground, not the air in any home.
Local help
Hardin County, Local resources
Radon testing and mitigation in Hardin County
- Radon Education and Licensing ProgramRadon Education and Licensing Program, run by Ohio Department of Health, licenses or certifies radon professionals and offers free or discounted test kits, and answers questions about testing and mitigation in Ohio.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
Free radon test kits are available for Ohio homeowners.
- Compare kits
- Professionals in Ohio479 professionals are listed in Ohio.
What Ohio's program says
- Phone
- 614-728-0272
- indoor.radon@odh.ohio.gov
- Licensing of radon professionals
This program licenses companies and persons directly involved with the radon testing and mitigation industry.
What it means
Hardin County, Questions
Questions about radon in Hardin County
Are radon levels high in Hardin County?
Over the 2008 to 2017 laboratory totals, 43.3% of the radon tests reported to CDC for Hardin County, Ohio were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.4 pCi/L. Of 79 Ohio counties with 30 or more tests for the same period, 61 reported a higher share; pooled, the state comes to 52.3%.
Which counties border Hardin County?
Hardin County borders 7 counties: Logan County, Wyandot County, Marion County, Union County, Allen County, Hancock County and Auglaize County.
Products
Hardin County, Products
Testing a home in Hardin County
In Hardin County, 43.3% of 67 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 52.3% pooled across Ohio. In Zone 1 the year-round level in Hardin 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
lüft plug-in radon and indoor air quality monitor
- C-NRPP 2024/25: Approved
- Plug-in
- Wi-Fi, Bluetooth
- App only
First reading: Within 90 minutes
Short-term kitempowerDX
Standard Radon Test short-term mail-in radon test kit
- Lab fee included
Method: Passive sampler
In home: 48 to 96 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Hardin County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Hardin County
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Hardin County, Bordering counties
Counties bordering Hardin County
Calculated by Radon411- Radon levels in Logan CountyEPA zone 1
73.6%at or above 4 pCi/L
Median 7.9 pCi/L · 755 tests · 30.3 points above Hardin County
- Radon levels in Auglaize CountyEPA zone 1
71.2%at or above 4 pCi/L
Median 6.5 pCi/L · 139 tests · 27.9 points above Hardin County
- Radon levels in Marion CountyEPA zone 1
65.3%at or above 4 pCi/L
Median 6.4 pCi/L · 265 tests · 22.0 points above Hardin County
- Radon levels in Union CountyEPA zone 1
60.2%at or above 4 pCi/L
Median 4.8 pCi/L · 1,285 tests · 16.9 points above Hardin County
- Radon levels in Allen CountyEPA zone 1
56.7%at or above 4 pCi/L
Median 5.0 pCi/L · 238 tests · 13.4 points above Hardin County
- Radon levels in Wyandot CountyEPA zone 1
46.3%at or above 4 pCi/L
Median 3.6 pCi/L · 320 tests · 3.0 points above Hardin County
- Radon levels in Hancock CountyEPA zone 1
46.2%at or above 4 pCi/L
Median 3.7 pCi/L · 1,382 tests · 2.9 points above Hardin County
Hardin County, Cities and towns
Cities and towns in Hardin County
About 30,072 people live in Hardin County by the Census Bureau's estimate for July 1, 2025, 652 fewer than in 2020 (−2.1%). That works out to 64 people per square mile of land. Its largest town, Kenton, has 7,808 residents, 26.0% of the total. Reported testing is thin here: 67 tests over 2008 to 2017, or 2.2 for every 1,000 residents (2025 estimate), where Ohio as a whole comes to 8.3.
From Kenton to Patterson, CDC publishes no figure by town: each reads Hardin County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Kenton | 7,808 | −1.9% | 26.0% |
| Ada | 4,985 | −6.4% | 16.6% |
| Forest | 1,332 | −1.7% | 4.4% |
| Alger | 827 | −1.9% | 2.8% |
| Dunkirk | 753 | −2.5% | 2.5% |
| Mount Victory | 595 | −1.7% | 2.0% |
| McGuffey | 454 | −1.9% | 1.5% |
| Ridgewayextends beyond Hardin County | 312 | −1.3% | Counted whole |
| Patterson | 128 | −1.5% | 0.4% |
9 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). A place that extends beyond Hardin County is counted whole, so it has no share.
Hardin County, Homes
Homes in Hardin County
Hardin County is a place of houses on their own lots: 75% of its 12,921 homes are detached single-family houses, against 69% across Ohio. Half of its homes were built before 1969, close to Ohio's 1970: 41% date from before 1960 and 13% from 2000 or later. 73% of occupied homes are lived in by their owner (Ohio: 67%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Hardin County | Ohio |
|---|---|---|
| Housing units | 12,921 | 5,271,573 |
| Detached houses | 75% | 69% |
| In buildings of 5 or more | 7% | 15% |
| Mobile homes | 11% | 4% |
| Built before 1960 | 41% | 38% |
| Built since 2000 | 13% | 16% |
| Middle year built | 1969 | 1970 |
| Owner-occupied | 73% | 67% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.