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 Richland County, Ohio
EPA puts Richland County in Zone 1, its highest radon zone, and high results are common there: 62.2% of the 1,327 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
62.2%
9.9 pts above OH
- Richland
- 62.2%
- Ohio
- 52.3%
1,327 tests, 2008 to 2017
Median result
5.2pCi/L
Action level reached
- Richland
- 5.2 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
1,327
23rd of 79 by tests
- Richland
- 1,327
- 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
20 of 79
Top quarter
- Richland
- 62.2%
- Pickaway
- 81.4%
By share, of 79 with 30+ tests
Read a result for Richland County
Starts at Richland County's median, 5.2 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 5.2 pCi/L
At or above 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is at or above 4 pCi/L. EPA recommends fixing a home when the radon level is 4 pCi/L or higher. Richland County's median reported result, 2008 to 2017.
The data
Richland County, At a glance
Richland County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Richland County in
USGS geologic potential: High across 94% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Richland County, 2008 to 2017, laboratory
Under 2 pCi/L: 15%2 to 4 pCi/L: 23%4 pCi/L and above: 62%
Of 1,327 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 196 | 14.8% |
| 2 to 4 pCi/L | 306 | 23.1% |
| 4 pCi/L and above | 825 | 62.2% |
What these figures count
These are the 1,327 tests reported to CDC for Richland 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).
Richland County, Compared
Richland County radon figures, compared
Calculated by Radon411More than half: 62.2% of the 1,327 radon tests reported to CDC for Richland County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 20th of 79 Ohio counties with 30 or more tests for the same period. That is 9.9 points above the 52.3% pooled from 88 Ohio counties.
The median result, 5.2 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 371.3 pCi/L. The rest split 14.8% under 2 pCi/L and 23.1% from 2 to 4 (Ohio: 23.1% and 24.6%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 62.2% share point the same way here.
3 of its 5 bordering counties with figures ran higher, led by Knox County at 72.0%; Huron County reported 59.4%. Statewide for the same period, Pickaway County reported the highest share (81.4%) and Cuyahoga County the lowest (21.7%).
CDC's ten-year totals for Richland County went from 1,415 tests (2005 to 2014) to 1,327 (2008 to 2017), the share going from 61.3% to 62.2%.
Nationally, every county with a figure for the same period pools to 35.7%; Richland County sits 26.5 points above it. CDC also counts 156 tests taken after mitigation in Richland County for the same period: tests in homes where a fix was already in.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Richland County, Geology
The ground under Richland County
PredictedMost of the ground under Richland County is one class on USGS's geologic map: 93.7% of its land is high radon potential, with 6.3% moderate. The map puts 45.4% of Richland County in the area it calls Till Plains and 34.6% in Area of Elevated Radioactivity, with 2 smaller areas beside them. USGS gives the first a radon index of 14 and the second 12, both 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 | 45.4% |
| Area of Elevated Radioactivity | Pennsylvanian shale, sandstone, coal, and limestone. | High | 12 | 34.6% |
| Glaciated Plateau | Pre-Wisconsin glacial deposits derived from high radioactivity marine black shale. | High | 12 | 13.7% |
| Glaciated Plateau | Devonian, Mississippian and Permian carbonates and shales. | Moderate | 11 | 6.3% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Richland County beside the ground around it
Richland County has more high-potential ground than Ohio as a whole: 93.7% of its land against 62.8%. Of the 5 counties that border it, 3 have more high-potential ground, Crawford County the most at 100%.
The map rates the ground, not the air in any home.
Local help
Richland County, Local resources
Radon testing and mitigation in Richland County
Listed radon businesses with an address in Richland 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.
Listed radon professionals by town: Mansfield, Galion, Lexington
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
Richland County, Questions
Questions about radon in Richland County
Are radon levels high in Richland County?
Over the 2008 to 2017 laboratory totals, 62.2% of the radon tests reported to CDC for Richland County, Ohio were at or above 4 pCi/L, and the median reported pre-mitigation result was 5.2 pCi/L. Of 79 Ohio counties with 30 or more tests for the same period, 19 reported a higher share; pooled, the state comes to 52.3%.
Which counties border Richland County?
Richland County borders 5 counties: Ashland County, Crawford County, Morrow County, Knox County and Huron County.
Products
Richland County, Products
Testing a home in Richland County
In Richland County, 62.2% of 1,327 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 Richland 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
MonitorX-Sense
XR0A-SR battery digital radon detector with a screen
- C-NRPP 2024/25: Not included
- Battery
- Screen
Method: Alpha spectrometry
First reading: Within 24 hours
Short-term kit
RA100 short-term liquid scintillation radon test kit
- Lab fee extra
Method: Liquid scintillation
In home: 48 to 96 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Richland County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Richland County
Explore
Richland County, Bordering counties
Counties bordering Richland County
Calculated by Radon411- Radon levels in Knox CountyEPA zone 1
72.0%at or above 4 pCi/L
Median 8.1 pCi/L · 1,530 tests · 9.8 points above Richland County
- Radon levels in Morrow CountyEPA zone 1
65.0%at or above 4 pCi/L
Median 5.7 pCi/L · 177 tests · 2.8 points above Richland County
- Radon levels in Ashland CountyEPA zone 1
62.9%at or above 4 pCi/L
Median 5.4 pCi/L · 340 tests · 0.7 points above Richland County
- Radon levels in Crawford CountyEPA zone 1
59.5%at or above 4 pCi/L
Median 4.7 pCi/L · 210 tests · 2.7 points below Richland County
- Radon levels in Huron CountyEPA zone 1
59.4%at or above 4 pCi/L
Median 4.9 pCi/L · 796 tests · 2.8 points below Richland County
Richland County, Cities and towns
Cities and towns in Richland County
Richland County's population has barely moved since 2020: 124,893 residents on July 1, 2025 against 124,969 then, by the Census Bureau's estimates. That works out to 252 people per square mile of land. Its largest town, Mansfield, has 47,381 residents, 37.9% of the total. CDC's 1,327 reported tests for 2008 to 2017 work out to 10.6 per 1,000 residents (2025 estimate), close to Ohio's 8.3.
From Mansfield to Lucas, CDC publishes no figure by town: each reads Richland County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Mansfield | 47,381 | −0.2% | 37.9% |
| Galionextends beyond Richland County | 10,370 | −0.7% | Counted whole |
| Shelby | 9,231 | −0.6% | 7.4% |
| Ontario | 6,692 | Level | 5.4% |
| Lexington | 4,848 | Level | 3.9% |
| Crestlineextends beyond Richland County | 4,487 | −0.8% | Counted whole |
| Bellville | 2,013 | +2.6% | 1.6% |
| Plymouthextends beyond Richland County | 1,702 | −0.9% | Counted whole |
| Butler | 929 | −0.4% | 0.7% |
| Shiloh | 615 | −0.5% | 0.5% |
| Lucas | 586 | −0.5% | 0.5% |
11 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 Richland County is counted whole, so it has no share.
Richland County, Homes
Homes in Richland County
Of Richland County's 54,616 homes, 74% are detached houses, against 69% across Ohio; 9% are in buildings of five or more homes. Half of its homes were built before 1964, close to Ohio's 1970: 44% date from before 1960 and 10% from 2000 or later. 68% 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 | Richland County | Ohio |
|---|---|---|
| Housing units | 54,616 | 5,271,573 |
| Detached houses | 74% | 69% |
| In buildings of 5 or more | 9% | 15% |
| Mobile homes | 4% | 4% |
| Built before 1960 | 44% | 38% |
| Built since 2000 | 10% | 16% |
| Middle year built | 1964 | 1970 |
| Owner-occupied | 68% | 67% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.