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 Valley County, Idaho
EPA puts Valley County in Zone 1, its highest radon zone, and 27.3% of its 128 reported radon tests (2008 to 2017, laboratory totals) were 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
27.3%
14.2 pts below ID
- Valley
- 27.3%
- Idaho
- 41.5%
128 tests, 2008 to 2017
Median result
2.3pCi/L
Below action level
- Valley
- 2.3 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
128
16th of 37 by tests
- Valley
- 128
- Ada
- 3,030
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 Idaho
23 of 37
Middle half
- Valley
- 27.3%
- Bear Lake
- 78.1%
By share, of 37 with 30+ tests
Read a result for Valley County
Starts at Valley County's median, 2.3 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 2.3 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. Valley County's median reported result, 2008 to 2017.
The data
Valley County, At a glance
Valley County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Valley 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 Valley County, 2008 to 2017, laboratory
Under 2 pCi/L: 40%2 to 4 pCi/L: 33%4 pCi/L and above: 27%
Of 128 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 51 | 39.8% |
| 2 to 4 pCi/L | 42 | 32.8% |
| 4 pCi/L and above | 35 | 27.3% |
What these figures count
These are the 128 tests reported to CDC for Valley 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).
Valley County, Compared
Valley County radon figures, compared
Calculated by Radon411Valley County's 128 reported tests over the 2008 to 2017 laboratory totals had a middle value of 2.3 pCi/L and a maximum of 77.8 pCi/L, and 27.3% reached 4 pCi/L. Idaho as a whole (44 Idaho counties, pooled) comes to 41.5%: 14.2 points higher than here.
Among its state's counties it ranks 23rd of 37 Idaho counties with 30 or more tests for the same period. Statewide for the same period, Bear Lake County reported the highest share (78.1%) and Payette County the lowest (4.9%).
Below the action level, 51 tests (39.8%) came in under 2 pCi/L, against 31.5% statewide, and 42 tests (32.8%) fell between 2 and 4, against 26.9% statewide. CDC's ten-year totals for Valley County went from 97 tests (2005 to 2014) to 128 (2008 to 2017), the share going from 25.8% to 27.3%.
EPA's 1993 zone map puts Valley County in Zone 1, a predicted county average above 4 pCi/L. USGS geology rates 100% of the county's land high radon potential.
Next door, the shares run from 20.2% in Gem County to 72.7% in Custer County, with Boise County and Gem County below Valley County.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Valley County, Geology
The ground under Valley County
PredictedUSGS's geologic map puts all of Valley County's mapped land in one class: high radon potential. All of it lies in the area the map calls Northern Rocky Mountain Province, to which USGS gives a radon index of 12, in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Northern Rocky Mountain Province | Diorite and granite of the Idaho batholith. | High | 12 | 100% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Valley County beside the ground around it
Valley County has more high-potential ground than Idaho as a whole: 100% of its land against 50.7%. Of the 6 counties that border it, none has as large a share of high-potential ground; Custer County comes nearest at 100%.
The map rates the ground, not the air in any home.
Local help
Valley County, Local resources
Radon testing and mitigation in Valley 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
Valley County, Questions
Questions about radon in Valley County
Are radon levels high in Valley County?
Over the 2008 to 2017 laboratory totals, 27.3% of the radon tests reported to CDC for Valley County, Idaho were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.3 pCi/L. Of 37 Idaho counties with 30 or more tests for the same period, 22 reported a higher share; pooled, the state comes to 41.5%.
Which counties border Valley County?
Valley County borders 6 counties: Gem County, Adams County, Boise County, Custer County, Lemhi County and Idaho County.
Products
Valley County, Products
Testing a home in Valley County
In Valley County, 27.3% of 128 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 41.5% pooled across Idaho. In Zone 1 the year-round level in Valley 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
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
Short-term kit
Air Chek Short-Term radon test kit you hang, lab fee included
- Lab fee included
In home: 72 to 168 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Valley County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Valley County
Explore
Valley County, Bordering counties
Counties bordering Valley County
Calculated by Radon411- Radon levels in Custer CountyEPA zone 1
72.7%at or above 4 pCi/L
Median 6.8 pCi/L · 33 tests · 45.4 points above Valley County
- Radon levels in Lemhi CountyEPA zone 1
65.2%at or above 4 pCi/L
Median 5.2 pCi/L · 112 tests · 37.9 points above Valley County
- Radon levels in Adams CountyEPA zone 3
51.6%at or above 4 pCi/L
Median 4.0 pCi/L · 31 tests · 24.3 points above Valley County
- Radon levels in Idaho CountyEPA zone 1
40.0%at or above 4 pCi/L
Median 2.9 pCi/L · 90 tests · 12.7 points above Valley County
- Radon levels in Boise CountyEPA zone 1
22.4%at or above 4 pCi/L
Median 2.0 pCi/L · 58 tests · 4.9 points below Valley County
- Radon levels in Gem CountyEPA zone 3
20.2%at or above 4 pCi/L
Median 1.9 pCi/L · 99 tests · 7.1 points below Valley County
Valley County, Cities and towns
Cities and towns in Valley County
Valley County is growing: the Census Bureau puts it at 12,831 residents on July 1, 2025, up 8.4% from 11,841 in 2020. Spread over its land, that is 3.5 people to the square mile. Its largest town, McCall, has 4,133 residents, 32.2% of the total. Together its 3 incorporated places hold 42.1% of those residents; the other 57.9% live outside any of them. Testing is reported here more often than across the state: CDC's 128 reported tests for 2008 to 2017 come to 10.0 for every 1,000 residents (2025 estimate), against 6.4 for Idaho.
From McCall to Donnelly, CDC publishes no figure by town: each reads Valley County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| McCall | 4,133 | +11.2% | 32.2% |
| Cascade | 1,018 | +1.5% | 7.9% |
| Donnelly | 255 | +0.4% | 2.0% |
3 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).
Valley County, Homes
Homes in Valley County
Valley County is a place of houses on their own lots: 83% of its 12,601 homes are detached single-family houses, against 74% across Idaho. Half of its homes were built before 1993, close to Idaho's 1990: 8% date from before 1960 and 35% from 2000 or later. Owners live in 86% of the occupied homes (Idaho: 72%), so for most households a test and a fix are their own to order.
| Homes | Valley County | Idaho |
|---|---|---|
| Housing units | 12,601 | 776,683 |
| Detached houses | 83% | 74% |
| In buildings of 5 or more | 5% | 9% |
| Mobile homes | 8% | 7% |
| Built before 1960 | 8% | 18% |
| Built since 2000 | 35% | 35% |
| Middle year built | 1993 | 1990 |
| Owner-occupied | 86% | 72% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.