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 Allen County, Ohio
EPA puts Allen County in Zone 1, its highest radon zone, and high results are common there: 56.7% of the 238 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
56.7%
4.4 pts above OH
- Allen
- 56.7%
- Ohio
- 52.3%
238 tests, 2008 to 2017
Median result
5.0pCi/L
Action level reached
- Allen
- 5.0 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
238
53rd of 79 by tests
- Allen
- 238
- 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
37 of 79
Middle half
- Allen
- 56.7%
- Pickaway
- 81.4%
By share, of 79 with 30+ tests
Read a result for Allen County
Starts at Allen County's median, 5.0 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 5.0 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. Allen County's median reported result, 2008 to 2017.
The data
Allen County, At a glance
Allen County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Allen 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 Allen County, 2008 to 2017, laboratory
Under 2 pCi/L: 15%2 to 4 pCi/L: 28%4 pCi/L and above: 57%
Of 238 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 37 | 15.5% |
| 2 to 4 pCi/L | 66 | 27.7% |
| 4 pCi/L and above | 135 | 56.7% |
What these figures count
These are the 238 tests reported to CDC for Allen 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).
Allen County, Compared
Allen County radon figures, compared
Calculated by Radon411More than half: 56.7% of the 238 radon tests reported to CDC for Allen County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 37th of 79 Ohio counties with 30 or more tests for the same period. That is 4.4 points above the 52.3% pooled from 88 Ohio counties.
The median result, 5.0 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 57.2 pCi/L. The rest split 15.5% under 2 pCi/L and 27.7% from 2 to 4 (Ohio: 23.1% and 24.6%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 56.7% share point the same way here.
2 of its 4 bordering counties with figures ran higher, led by Auglaize County at 71.2%; Hardin County reported 43.3%. 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 Allen County went from 207 tests (2005 to 2014) to 238 (2008 to 2017), the share going from 54.6% to 56.7%.
Nationally, every county with a figure for the same period pools to 35.7%; Allen County sits 21.0 points above it. CDC also counts 6 tests taken after mitigation in Allen 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.
Allen County, Geology
The ground under Allen County
PredictedUSGS's geologic map puts all of Allen 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.
Allen County beside the ground around it
Allen County has more high-potential ground than Ohio as a whole: 100% of its land against 62.8%. Of the 5 counties that border it, none has as large a share of high-potential ground; Auglaize County comes nearest at 100%.
The map rates the ground, not the air in any home.
Local help
Allen County, Local resources
Radon testing and mitigation in Allen County
Listed radon businesses with an address in Allen 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: Lima, Bluffton
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
Allen County, Questions
Questions about radon in Allen County
Are radon levels high in Allen County?
Over the 2008 to 2017 laboratory totals, 56.7% of the radon tests reported to CDC for Allen County, Ohio were at or above 4 pCi/L, and the median reported pre-mitigation result was 5.0 pCi/L. Of 79 Ohio counties with 30 or more tests for the same period, 36 reported a higher share; pooled, the state comes to 52.3%.
Which counties border Allen County?
Allen County borders 5 counties: Auglaize County, Putnam County, Van Wert County, Hardin County and Hancock County.
Products
Allen County, Products
Testing a home in Allen County
In Allen County, 56.7% of 238 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 Allen 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
XR0B-SR battery digital radon monitor with an alarm
- C-NRPP 2024/25: Not included
- Battery
- Alarm
- Screen
Method: Alpha spectrometry
First reading: Within 24 hours
Short-term kit
RA400 short-term liquid scintillation radon test kit, lab fee included
- Lab fee included
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
Allen County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Allen County
Explore
Allen County, Bordering counties
Counties bordering Allen County
Calculated by Radon411- Radon levels in Auglaize CountyEPA zone 1
71.2%at or above 4 pCi/L
Median 6.5 pCi/L · 139 tests · 14.5 points above Allen County
- Radon levels in Putnam CountyEPA zone 2
59.6%at or above 4 pCi/L
Median 4.8 pCi/L · 94 tests · 2.9 points above Allen County
- Radon levels in Van Wert CountyEPA zone 1
53.8%at or above 4 pCi/L
Median 4.3 pCi/L · 26 tests · 2.9 points below Allen County
- Radon levels in Hancock CountyEPA zone 1
46.2%at or above 4 pCi/L
Median 3.7 pCi/L · 1,382 tests · 10.5 points below Allen County
- Radon levels in Hardin CountyEPA zone 1
43.3%at or above 4 pCi/L
Median 3.4 pCi/L · 67 tests · 13.4 points below Allen County
Allen County, Cities and towns
Cities and towns in Allen County
About 100,881 people live in Allen County by the Census Bureau's estimate for July 1, 2025, 1,235 fewer than in 2020 (−1.2%). That works out to 251 people per square mile of land. Its largest town, Lima, has 34,695 residents, 34.4% of the total. Reported testing is thin here: 238 tests over 2008 to 2017, or 2.4 for every 1,000 residents (2025 estimate), where Ohio as a whole comes to 8.3.
From Lima to Beaverdam, CDC publishes no figure by town: each reads Allen County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Lima | 34,695 | −2.2% | 34.4% |
| Delphosextends beyond Allen County | 7,096 | −0.3% | Counted whole |
| Blufftonextends beyond Allen County | 3,875 | −2.2% | Counted whole |
| Spencerville | 2,165 | −1.8% | 2.1% |
| Elida | 1,904 | −0.8% | 1.9% |
| Cairo | 507 | −1.9% | 0.5% |
| Harrod | 426 | +0.5% | 0.4% |
| Lafayette | 401 | −1.2% | 0.4% |
| Beaverdam | 311 | −2.5% | 0.3% |
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 Allen County is counted whole, so it has no share.
Allen County, Homes
Homes in Allen County
Allen County is a place of houses on their own lots: 77% of its 44,697 homes are detached single-family houses, against 69% across Ohio. Half of its homes were built before 1965, close to Ohio's 1970: 44% date from before 1960 and 9% 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 | Allen County | Ohio |
|---|---|---|
| Housing units | 44,697 | 5,271,573 |
| Detached houses | 77% | 69% |
| In buildings of 5 or more | 8% | 15% |
| Mobile homes | 4% | 4% |
| Built before 1960 | 44% | 38% |
| Built since 2000 | 9% | 16% |
| Middle year built | 1965 | 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.