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
Locations and reports
Radon Levels in Jefferson County, Idaho
EPA puts Jefferson County in Zone 2, its middle radon zone, and high results are common there: 67.1% of the 207 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
67.1%
25.6 pts above ID
- Jefferson
- 67.1%
- Idaho
- 41.5%
207 tests, 2008 to 2017
Median result
5.7pCi/L
Action level reached
- Jefferson
- 5.7 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
207
12th of 37 by tests
- Jefferson
- 207
- Ada
- 3,030
Reported to CDC before any fix, 2008 to 2017
EPA radon zone
Zone 2
Moderate potential
- 1
- Zone 2
- 3
1 highest, 3 lowest
EPA predicts 2 to 4 pCi/L indoors
Rank in Idaho
3 of 37
Top quarter
- Jefferson
- 67.1%
- Bear Lake
- 78.1%
By share, of 37 with 30+ tests
Read a result for Jefferson County
Starts at Jefferson County's median, 5.7 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 5.7 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. Jefferson County's median reported result, 2008 to 2017.
The data
Jefferson County, At a glance
Jefferson County at a glance
Predicted: EPA radon zone
EPA Zone 2: moderate predicted potential
Jefferson County is a
USGS geologic potential: Moderate across 99% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Jefferson County, 2008 to 2017, laboratory
Under 2 pCi/L: 12%2 to 4 pCi/L: 21%4 pCi/L and above: 67%
Of 207 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 24 | 11.6% |
| 2 to 4 pCi/L | 44 | 21.3% |
| 4 pCi/L and above | 139 | 67.1% |
What these figures count
These are the 207 tests reported to CDC for Jefferson 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).
Jefferson County, Compared
Jefferson County radon figures, compared
Calculated by Radon411More than half: 67.1% of the 207 radon tests reported to CDC for Jefferson County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 3rd of 37 Idaho counties with 30 or more tests for the same period. That is 25.6 points above the 41.5% pooled from 44 Idaho counties.
The median result, 5.7 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 68.0 pCi/L. The rest split 11.6% under 2 pCi/L and 21.3% from 2 to 4 (Idaho: 31.5% and 26.9%). The reported tests do not follow EPA's Zone 2 label for Jefferson County (predicted average between 2 and 4 pCi/L): 67.1% of them reached 4 pCi/L, fewer than that label suggests.
No bordering county with a figure for the same period reported a higher share; the closest is Madison County at 63.7%, the lowest Bonneville County at 40.1%. Statewide for the same period, Bear Lake County reported the highest share (78.1%) and Payette County the lowest (4.9%).
CDC's ten-year totals for Jefferson County went from 169 tests (2005 to 2014) to 207 (2008 to 2017), the share going from 61.5% to 67.1%.
Nationally, every county with a figure for the same period pools to 35.7%; Jefferson County sits 31.4 points above it. CDC also counts 9 tests taken after mitigation in Jefferson 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.
Jefferson County, Geology
The ground under Jefferson County
PredictedMost of the ground under Jefferson County is one class on USGS's geologic map: 99.2% of its land is moderate radon potential, with 0.8% high. 99.2% of it lies in the area the map calls Eastern Snake river plain and Malheur-Boise-King Section, to which USGS gives a radon index of 10, in the moderate band (9 to 11).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Eastern Snake river plain and Malheur-Boise-King Section | Basalt flows. | Moderate | 10 | 99.2% |
| Middle Rocky Mts./Yellowstone | Extrusive volcanics, rhyolite flows, variable composition. | High | 12 | 0.8% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Jefferson County beside the ground around it
Idaho as a whole has more high-potential ground than Jefferson County: 50.7% of its land, against 0.8% here. Of the 6 counties that border it, 5 have more high-potential ground, Fremont County the most at 68.2%.
The map rates the ground, not the air in any home.
Local help
Jefferson County, Local resources
Radon testing and mitigation in Jefferson County
- DHW Environmental Health ProgramDHW Environmental Health Program, run by Idaho Department of Health and Welfare, offers free or discounted test kits, and answers questions about testing and mitigation in Idaho.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
Order a free radon test kit.
- Compare kits
- See the Idaho directoryNo professionals are listed in Idaho yet. The state program can point you to registered testers and mitigators.
What Idaho's program says
- Phone
- 800-445-8647
- radon@dhw.idaho.gov
What it means
Jefferson County, Questions
Questions about radon in Jefferson County
Are radon levels high in Jefferson County?
Over the 2008 to 2017 laboratory totals, 67.1% of the radon tests reported to CDC for Jefferson County, Idaho were at or above 4 pCi/L, and the median reported pre-mitigation result was 5.7 pCi/L. Of 37 Idaho counties with 30 or more tests for the same period, 2 reported a higher share; pooled, the state comes to 41.5%.
Which counties border Jefferson County?
Jefferson County borders 6 counties: Clark County, Madison County, Butte County, Bingham County, Fremont County and Bonneville County.
Products
Jefferson County, Products
Testing a home in Jefferson County
In Jefferson County, 67.1% of 207 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 41.5% pooled across Idaho. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Jefferson County; a long-term test tells the year-round average.
Test kits and monitors3
See every kit and monitor
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
Monitor
EcoQube Wi-Fi continuous radon monitor
- C-NRPP 2024/25: Approved
- Plug-in
- Wi-Fi
- App only
Method: Ion chamber
First reading: Within 10 minutes
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Jefferson County, Bordering counties
Counties bordering Jefferson County
Calculated by Radon411- Radon levels in Butte CountyEPA zone 1
75.9%at or above 4 pCi/L
Median 12.8 pCi/L · 29 tests · 8.8 points above Jefferson County
- Radon levels in Clark CountyEPA zone 1
75.0%at or above 4 pCi/L
Median 14.1 pCi/L · 4 tests · 7.9 points above Jefferson County
- Radon levels in Madison CountyEPA zone 2
63.7%at or above 4 pCi/L
Median 6.2 pCi/L · 314 tests · 3.4 points below Jefferson County
- Radon levels in Bingham CountyEPA zone 2
52.0%at or above 4 pCi/L
Median 4.2 pCi/L · 446 tests · 15.1 points below Jefferson County
- Radon levels in Fremont CountyEPA zone 1
49.5%at or above 4 pCi/L
Median 3.9 pCi/L · 101 tests · 17.6 points below Jefferson County
- Radon levels in Bonneville CountyEPA zone 2
40.1%at or above 4 pCi/L
Median 3.4 pCi/L · 1,117 tests · 27.0 points below Jefferson County
Jefferson County, Cities and towns
Cities and towns in Jefferson County
Jefferson County is growing: the Census Bureau puts it at 35,297 residents on July 1, 2025, up 13.6% from 31,080 in 2020. That works out to 32 people per square mile of land. No town dominates: Rigby, the largest, has 5,757 residents, 16.3% of the total. CDC's 207 reported tests for 2008 to 2017 work out to 5.9 per 1,000 residents (2025 estimate), close to Idaho's 6.4.
From Rigby to Hamer, CDC publishes no figure by town: each reads Jefferson County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Rigby | 5,757 | +13.6% | 16.3% |
| Menan | 719 | +1.6% | 2.0% |
| Ririeextends beyond Jefferson County | 711 | +6.3% | Counted whole |
| Roberts | 572 | +15.3% | 1.6% |
| Lewisville | 437 | +5.6% | 1.2% |
| Mud Lake | 364 | +14.5% | 1.0% |
- Hamer
7 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. “(part)” marks a place that extends into another county. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025). A place that extends beyond Jefferson County is counted whole, so it has no share.
Jefferson County, Homes
Homes in Jefferson County
Jefferson County is a place of houses on their own lots: 85% of its 10,499 homes are detached single-family houses, against 74% across Idaho. Half of its homes were built before 1991, close to Idaho's 1990: 20% date from before 1960 and 42% from 2000 or later. Owners live in 82% of the occupied homes (Idaho: 72%), so for most households a test and a fix are their own to order.
| Homes | Jefferson County | Idaho |
|---|---|---|
| Housing units | 10,499 | 776,683 |
| Detached houses | 85% | 74% |
| In buildings of 5 or more | 2% | 9% |
| Mobile homes | 7% | 7% |
| Built before 1960 | 20% | 18% |
| Built since 2000 | 42% | 35% |
| Middle year built | 1991 | 1990 |
| Owner-occupied | 82% | 72% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.