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 Putnam County, Illinois
EPA puts Putnam County in Zone 1, its highest radon zone, and high results are common there: 53.3% of the 45 radon tests reported to CDC (2017) 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
53.3%
19.6 pts above IL
- Putnam
- 53.3%
- Illinois
- 33.7%
45 tests, 2017
Median result
4.5pCi/L
Action level reached
- Putnam
- 4.5 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2017
Tests reported
45
61st of 70 by tests
- Putnam
- 45
- Cook
- 26,937
Reported to CDC before any fix, 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 Illinois
16 of 70
Top quarter
- Putnam
- 53.3%
- Stark
- 69.2%
By share, of 70 with 30+ tests
Read a result for Putnam County
Starts at Putnam County's median, 4.5 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 4.5 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. Putnam County's median reported result, 2017.
The data
Putnam County, At a glance
Putnam County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Putnam 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 Putnam County, 2017
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 100.0% |
| 2015 | 100.0% |
| 2017 | 53.3% |
2017: 53.3%. Across these years the share ran from 53.3% to 100.0%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
These are the 45 tests reported to CDC for Putnam County over 2017, 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: 2017. Measured data period: 2005 to 2017 (every CDC figure on file).
Putnam County, Compared
Putnam County radon figures, compared
Calculated by Radon411More than half: 53.3% of the 45 radon tests reported to CDC for Putnam County in 2017 read at least 4 pCi/L. That places it 16th of 70 Illinois counties with 30 or more tests for the same period. That is 19.6 points above the 33.7% pooled from 93 Illinois counties.
The median result, 4.5 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 24.3 pCi/L. The rest split 26.7% under 2 pCi/L and 20.0% from 2 to 4 (Illinois: 37.7% and 28.6%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 53.3% share point the same way here.
1 of its 3 bordering counties with figures ran higher, led by Bureau County at 58.6%; LaSalle County reported 45.8%. Statewide for the same period, Stark County reported the highest share (69.2%) and Williamson County the lowest (8.4%).
The busiest year on file was 2014, with 54 tests reported; the quietest, 2015, had 33.
Over 3 years of annual figures the share fell 46.7 points, from 100.0% in 2014 to 53.3% in 2017; its peak was 100.0% in 2014. Nationally, every county with a figure for the same period pools to 31.7%; Putnam County sits 21.6 points above it.
Putnam CountyIllinois, pooled
53.3% % of tests33.7% % of tests
| Year | Tests | Putnam County, at or above 4 pCi/L | Illinois, pooled |
|---|---|---|---|
| 2014 | 54 | 100.0% | 37.8% |
| 2015 | 33 | 100.0% | 36.6% |
| 2017 | 45 | 53.3% | 33.7% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
Putnam County, Geology
The ground under Putnam County
PredictedUSGS's geologic map puts all of Putnam County's mapped land in one class: high radon potential. All of it lies in the area the map calls Bloomington Ridged Plain, to which USGS gives a radon index of 13, in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Bloomington Ridged Plain | Wisconsinan glacial deposits and loess over Paleozoic sedimentary rocks. | High | 13 | 100% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Putnam County beside the ground around it
Putnam County has more high-potential ground than Illinois as a whole: 100% of its land against 64.5%. Of the 3 counties that border it, none has as large a share of high-potential ground; LaSalle County comes nearest at 100%.
The map rates the ground, not the air in any home.
Local help
Putnam County, Local resources
Radon testing and mitigation in Putnam County
- IEMA-OHS Radon ProgramIEMA-OHS Radon Program, run by Illinois Emergency Management Agency and Office of Homeland Security, licenses or certifies radon professionals and states the rule for disclosing radon when a home is sold, and answers questions about testing and mitigation in Illinois.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsAsk the program whether it has free or discounted kits, or compare kits you can buy.
- Compare kits
- Professionals in Illinois339 professionals are listed in Illinois.
What Illinois's program says
- Phone
- (800) 325-1245
- Licensing of radon professionals
The Agency also licenses and regulates the individuals who provide radon measurement and mitigation to the public.
- Disclosure when a home is sold or rented
Illinois Radon Awareness Act - This is the legislation that requires the seller to provide to the buyer of any interest in residential real property the IEMA-OHS pamphlet entitled "Radon Testing Guidelines for Real Estate Transactions" and the Illinois Disclosure of Information on Radon Hazards.
What it means
Putnam County, Questions
Questions about radon in Putnam County
Are radon levels high in Putnam County?
In 2017, 53.3% of the radon tests reported to CDC for Putnam County, Illinois were at or above 4 pCi/L, and the median reported pre-mitigation result was 4.5 pCi/L. Of 70 Illinois counties with 30 or more tests for the same period, 15 reported a higher share; pooled, the state comes to 33.7%.
Which counties border Putnam County?
Putnam County borders 3 counties: Marshall County, Bureau County and LaSalle County.
Products
Putnam County, Products
Testing a home in Putnam County
In Putnam County, 53.3% of 45 tests reported to CDC in 2017 reached 4 pCi/L, against 33.7% pooled across Illinois. In Zone 1 the year-round level in Putnam 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
Hello Radon C battery radon monitor with an e-ink screen
- C-NRPP 2024/25: Not included
- Battery
- Screen
Method: Alpha spectrometry
First reading: Within 24 hours
Short-term kitFirst Alert
RD1 short-term charcoal radon test kit
- Lab fee included
Method: Charcoal
In home: 2 to 4 days
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Putnam County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Putnam County
Explore
Putnam County, Bordering counties
Counties bordering Putnam County
Calculated by Radon411- Radon levels in Bureau CountyEPA zone 1
58.6%at or above 4 pCi/L
Median 5.1 pCi/L · 333 tests · 5.3 points above Putnam County
- Radon levels in Marshall CountyEPA zone 1
48.1%at or above 4 pCi/L
Median 3.8 pCi/L · 81 tests · 5.2 points below Putnam County
- Radon levels in LaSalle CountyEPA zone 1
45.8%at or above 4 pCi/L
Median 3.6 pCi/L · 1,002 tests · 7.5 points below Putnam County
Putnam County, Cities and towns
Cities and towns in Putnam County
Putnam County's population has barely moved since 2020: 5,619 residents on July 1, 2025 against 5,624 then, by the Census Bureau's estimates. That works out to 35 people per square mile of land. Its largest town, Granville, has 1,325 residents, 23.6% of the total. Together its 6 incorporated places hold 59.2% of those residents; the other 40.8% live outside any of them. CDC's 45 reported tests for 2017 work out to 8.0 per 1,000 residents (2025 estimate), close to Illinois' 10.9.
From Granville to Standard, CDC publishes no figure by town: each reads Putnam County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Granville | 1,325 | −2.4% | 23.6% |
| Hennepin | 747 | −1.7% | 13.3% |
| Mark | 505 | −2.1% | 9.0% |
| McNabb | 273 | −2.2% | 4.9% |
| Magnolia | 256 | −0.4% | 4.6% |
| Standard | 221 | −2.6% | 3.9% |
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).
Putnam County, Homes
Homes in Putnam County
Putnam County is a place of houses on their own lots: 89% of its 3,069 homes are detached single-family houses, against 58% across Illinois. Half of its homes were built before 1975, close to Illinois' 1970: 33% date from before 1960 and 17% from 2000 or later. Owners live in 81% of the occupied homes (Illinois: 67%), so for most households a test and a fix are their own to order.
| Homes | Putnam County | Illinois |
|---|---|---|
| Housing units | 3,069 | 5,443,501 |
| Detached houses | 89% | 58% |
| In buildings of 5 or more | 1% | 22% |
| Mobile homes | 4% | 2% |
| Built before 1960 | 33% | 38% |
| Built since 2000 | 17% | 16% |
| Middle year built | 1975 | 1970 |
| Owner-occupied | 81% | 67% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.