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
Locations and reports
Radon Levels in Canyon County, Idaho
EPA puts Canyon County in Zone 2, its middle radon zone, and most reported tests there come back low, though 10.7% of 563 (2008 to 2017, laboratory totals) reached 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
10.7%
30.8 pts below ID
- Canyon
- 10.7%
- Idaho
- 41.5%
563 tests, 2008 to 2017
Median result
1.6pCi/L
Below action level
- Canyon
- 1.6 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
563
5th of 37 by tests
- Canyon
- 563
- 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
36 of 37
Lowest quarter
- Canyon
- 10.7%
- Bear Lake
- 78.1%
By share, of 37 with 30+ tests
Read a result for Canyon County
Starts at Canyon County's median, 1.6 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 1.6 pCi/L
Below 2 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is below 2 pCi/L, the level at which EPA says a fix should be considered. Canyon County's median reported result, 2008 to 2017.
The data
Canyon County, At a glance
Canyon County at a glance
Predicted: EPA radon zone
EPA Zone 2: moderate predicted potential
Canyon County is a
USGS geologic potential: Moderate across 100% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Canyon County, 2008 to 2017, laboratory
Under 2 pCi/L: 63%2 to 4 pCi/L: 26%4 pCi/L and above: 11%
Of 563 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 357 | 63.4% |
| 2 to 4 pCi/L | 146 | 25.9% |
| 4 pCi/L and above | 60 | 10.7% |
What these figures count
These are the 563 tests reported to CDC for Canyon 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).
Canyon County, Compared
Canyon County radon figures, compared
Calculated by Radon411Canyon County reports fewer high tests than Idaho overall. 10.7% of its 563 tests over the 2008 to 2017 laboratory totals were at or above 4 pCi/L. That is 30.8 points below the 41.5% pooled from 44 Idaho counties.
Ordered from highest share down, it comes 36th of 37 Idaho counties with 30 or more tests for the same period. Nationally, every county with a figure for the same period pools to 35.7%; Canyon County sits 25.0 points below it.
Next door, the shares run from 4.9% in Payette County to 25.2% in Ada County, with Payette County below Canyon County. Zone 2 on EPA's map (predicted average between 2 and 4 pCi/L) and a 10.7% share point the same way here.
Half the tests came in under 1.6 pCi/L and half over it; the single highest reached 62.8 pCi/L. The rest split 63.4% under 2 pCi/L and 25.9% from 2 to 4 (Idaho: 31.5% and 26.9%).
CDC's ten-year totals for Canyon County went from 558 tests (2005 to 2014) to 563 (2008 to 2017), the share going from 9.5% to 10.7%.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Canyon County, Geology
The ground under Canyon County
PredictedUSGS's geologic map puts all of Canyon County's mapped land in one class: moderate radon potential. All 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 | 100% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Canyon County beside the ground around it
Across Idaho 50.7% of the land is rated high; none of Canyon County's is. Of the 5 counties that border it, 3 have more high-potential ground, Gem County the most at 19.3%.
The map rates the ground, not the air in any home.
Local help
Canyon County, Local resources
Radon testing and mitigation in Canyon 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
Canyon County, Questions
Questions about radon in Canyon County
Are radon levels high in Canyon County?
Over the 2008 to 2017 laboratory totals, 10.7% of the radon tests reported to CDC for Canyon County, Idaho were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.6 pCi/L. Of 37 Idaho counties with 30 or more tests for the same period, 35 reported a higher share; pooled, the state comes to 41.5%.
Which counties border Canyon County?
Canyon County borders 5 counties: Ada County, ID, Payette County, ID, Gem County, ID, Malheur County, OR and Owyhee County, ID.
Products
Canyon County, Products
Testing a home in Canyon County
In Canyon County, 10.7% of 563 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 Canyon 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
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
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Canyon County, Bordering counties
Counties bordering Canyon County
Calculated by Radon411- Radon levels in Ada County, IDEPA zone 2
25.2%at or above 4 pCi/L
Median 2.4 pCi/L · 3,030 tests · 14.5 points above Canyon County
- Radon levels in Owyhee County, IDEPA zone 2
23.3%at or above 4 pCi/L
Median 2.1 pCi/L · 30 tests · 12.6 points above Canyon County
- Radon levels in Gem County, IDEPA zone 3
20.2%at or above 4 pCi/L
Median 1.9 pCi/L · 99 tests · 9.5 points above Canyon County
- Radon levels in Malheur County, OREPA zone 2
8.3%at or above 4 pCi/L
Median 2.0 pCi/L · 12 tests · 2.4 points below Canyon County
- Radon levels in Payette County, IDEPA zone 2
4.9%at or above 4 pCi/L
Median 1.5 pCi/L · 61 tests · 5.8 points below Canyon County
Canyon County, Cities and towns
Cities and towns in Canyon County
Canyon County is growing: the Census Bureau puts it at 275,123 residents on July 1, 2025, up 18.1% from 233,001 in 2020. That works out to 469 people per square mile of land. Its largest town, Nampa, has 120,384 residents, 43.8% of the total. Reported testing is thin here: 563 tests over 2008 to 2017, or 2.0 for every 1,000 residents (2025 estimate), where Idaho as a whole comes to 6.4.
From Nampa to Notus, CDC publishes no figure by town: each reads Canyon County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Nampa | 120,384 | +18.7% | 43.8% |
| Caldwell | 76,629 | +26.2% | 27.9% |
| Starextends beyond Canyon County | 20,874 | +81.7% | Counted whole |
| Middleton | 12,600 | +31.6% | 4.6% |
| Parma | 2,203 | +5.2% | 0.8% |
| Wilder | 1,734 | +8.6% | 0.6% |
| Greenleaf | 788 | −2.8% | 0.3% |
| Melba | 630 | +10.5% | 0.2% |
| Notus | 605 | −1.3% | 0.2% |
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 Canyon County is counted whole, so it has no share.
Canyon County, Homes
Homes in Canyon County
Canyon County is a place of houses on their own lots: 79% of its 85,583 homes are detached single-family houses, against 74% across Idaho. Much of Canyon County is recent building: 46% of its homes have gone up since 2000 and the middle year built is 1998, against 1990 for Idaho. Owners live in 75% of the occupied homes (Idaho: 72%), so for most households a test and a fix are their own to order.
| Homes | Canyon County | Idaho |
|---|---|---|
| Housing units | 85,583 | 776,683 |
| Detached houses | 79% | 74% |
| In buildings of 5 or more | 5% | 9% |
| Mobile homes | 7% | 7% |
| Built before 1960 | 16% | 18% |
| Built since 2000 | 46% | 35% |
| Middle year built | 1998 | 1990 |
| Owner-occupied | 75% | 72% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.