Short-term kitKidde
442020 short-term charcoal radon test kit
- Lab fee included
Method: Charcoal
In home: 3 days
Locations and reports
Radon Levels in Washington County, Idaho
EPA puts Washington County in Zone 3, its lowest radon zone, and 20.9% of its 67 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
20.9%
20.6 pts below ID
- Washington
- 20.9%
- Idaho
- 41.5%
67 tests, 2008 to 2017
Median result
2.1pCi/L
Below action level
- Washington
- 2.1 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
67
26th of 37 by tests
- Washington
- 67
- Ada
- 3,030
Reported to CDC before any fix, 2008 to 2017
EPA radon zone
Zone 3
Lower potential
- 1
- 2
- Zone 3
1 highest, 3 lowest
EPA predicts under 2 pCi/L indoors
Rank in Idaho
31 of 37
Lowest quarter
- Washington
- 20.9%
- Bear Lake
- 78.1%
By share, of 37 with 30+ tests
Read a result for Washington County
Starts at Washington County's median, 2.1 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 2.1 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. Washington County's median reported result, 2008 to 2017.
The data
Washington County, At a glance
Washington County at a glance
Predicted: EPA radon zone
EPA Zone 3: lower predicted potential
USGS geologic potential: Low across 88% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Washington County, 2008 to 2017, laboratory
Under 2 pCi/L: 45%2 to 4 pCi/L: 34%4 pCi/L and above: 21%
Of 67 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 30 | 44.8% |
| 2 to 4 pCi/L | 23 | 34.3% |
| 4 pCi/L and above | 14 | 20.9% |
What these figures count
These are the 67 tests reported to CDC for Washington 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).
Washington County, Compared
Washington County radon figures, compared
Calculated by Radon411Washington County's 67 reported tests over the 2008 to 2017 laboratory totals had a middle value of 2.1 pCi/L and a maximum of 47.7 pCi/L, and 20.9% reached 4 pCi/L. Idaho as a whole (44 Idaho counties, pooled) comes to 41.5%: 20.6 points higher than here.
Among its state's counties it ranks 31st 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, 30 tests (44.8%) came in under 2 pCi/L, against 31.5% statewide, and 23 tests (34.3%) fell between 2 and 4, against 26.9% statewide. CDC's ten-year totals for Washington County went from 65 tests (2005 to 2014) to 67 (2008 to 2017), the share going from 16.9% to 20.9%.
EPA's 1993 zone map puts Washington County in Zone 3, a predicted county average under 2 pCi/L. USGS geology rates 88% of the county's land low radon potential.
Next door, the shares run from 4.9% in Payette County to 51.6% in Adams County, with Gem County and Payette County below Washington County.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Washington County, Geology
The ground under Washington County
PredictedMost of the ground under Washington County is one class on USGS's geologic map: 88.1% of its land is low radon potential, with 11.9% moderate. The map puts 88.1% of Washington County in the area it calls Seven Devils and Tri-State Uplands and 11.6% in Eastern Snake river plain and Malheur-Boise-King Section. USGS gives the first a radon index of 8, in the low band (5 to 8), and the second 10, in the moderate band (9 to 11).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Seven Devils and Tri-State Uplands | Columbia River basalt flows. | Low | 8 | 88.1% |
| Eastern Snake river plain and Malheur-Boise-King Section | Basalt flows. | Moderate | 10 | 11.6% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Washington County beside the ground around it
Across Idaho 50.7% of the land is rated high; none of Washington 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
Washington County, Local resources
Radon testing and mitigation in Washington 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
Washington County, Questions
Questions about radon in Washington County
Are radon levels high in Washington County?
Over the 2008 to 2017 laboratory totals, 20.9% of the radon tests reported to CDC for Washington County, Idaho were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.1 pCi/L. Of 37 Idaho counties with 30 or more tests for the same period, 30 reported a higher share; pooled, the state comes to 41.5%.
Which counties border Washington County?
Washington County borders 5 counties: Adams County, ID, Gem County, ID, Payette County, ID, Baker County, OR and Malheur County, OR.
Products
Washington County, Products
Testing a home in Washington County
In Washington County, 20.9% of 67 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 41.5% pooled across Idaho. Zone 3 is the lowest label, yet homes at or above 4 pCi/L occur in every zone: a short-term kit (2 to 90 days) is the quick first check in Washington County.
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
MonitorSafetySiren
Pro4 plug-in radon detector with a display and alarm
- C-NRPP 2024/25: Not included
- Plug-in
- Alarm
- Screen
First reading: Within 48 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Washington County, Bordering counties
Counties bordering Washington County
Calculated by Radon411- Radon levels in Adams County, IDEPA zone 3
51.6%at or above 4 pCi/L
Median 4.0 pCi/L · 31 tests · 30.7 points above Washington County
- Radon levels in Baker County, OREPA zone 2
37.5%at or above 4 pCi/L
Median 2.4 pCi/L · 40 tests · 16.6 points above Washington County
- Radon levels in Gem County, IDEPA zone 3
20.2%at or above 4 pCi/L
Median 1.9 pCi/L · 99 tests · 0.7 points below Washington County
- Radon levels in Malheur County, OREPA zone 2
8.3%at or above 4 pCi/L
Median 2.0 pCi/L · 12 tests · 12.6 points below Washington County
- Radon levels in Payette County, IDEPA zone 2
4.9%at or above 4 pCi/L
Median 1.5 pCi/L · 61 tests · 16.0 points below Washington County
Washington County, Cities and towns
Cities and towns in Washington County
Washington County is growing: the Census Bureau puts it at 11,583 residents on July 1, 2025, up 9.7% from 10,556 in 2020. Spread over its land, that is 8.0 people to the square mile. Weiser alone is home to 6,249 of them, 53.9% of the total. Together its 3 incorporated places hold 58.9% of those residents; the other 41.1% live outside any of them. CDC's 67 reported tests for 2008 to 2017 work out to 5.8 per 1,000 residents (2025 estimate), close to Idaho's 6.4.
From Weiser to Midvale, CDC publishes no figure by town: each reads Washington County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Weiser | 6,249 | +10.5% | 53.9% |
| Cambridge | 357 | +2.0% | 3.1% |
| Midvale | 213 | +10.4% | 1.8% |
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).
Washington County, Homes
Homes in Washington County
Washington County is a place of houses on their own lots: 75% of its 4,586 homes are detached single-family houses, against 74% across Idaho. The homes are older than Idaho's as a whole: half were built before 1974 (1990 for Idaho), and 35% date from before 1960. 73% of occupied homes are lived in by their owner (Idaho: 72%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Washington County | Idaho |
|---|---|---|
| Housing units | 4,586 | 776,683 |
| Detached houses | 75% | 74% |
| In buildings of 5 or more | 4% | 9% |
| Mobile homes | 14% | 7% |
| Built before 1960 | 35% | 18% |
| Built since 2000 | 19% | 35% |
| Middle year built | 1974 | 1990 |
| Owner-occupied | 73% | 72% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.