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 Island County, Washington
EPA puts Island County in Zone 3, its lowest radon zone, and only 6 radon tests from it are on file with CDC (2020). Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Highest bordering
2.3%
Snohomish County
- Snohomish
- 2.3%
1 of 1 neighbours have 30+ tests, 2008 to 2017
Nearest county
4.9%
Kitsap County, 38 miles
- Kitsap
- 4.9%
- Washington
- 25.5%
Share at 4+ pCi/L, 82 tests, 2008 to 2017
Ground above low
None
52.7 pts below Washington
- Island
- 0.0%
- Washington
- 52.7%
Share of land USGS rates moderate or high potential
Tests reported
25
Too few for a share
- Island
- 25
- Needed
- 30
2016
EPA radon zone
Zone 3
Lower potential
- 1
- 2
- Zone 3
1 highest, 3 lowest
EPA predicts under 2 pCi/L indoors
Read a result for Island County
Starts at EPA's action level
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 4.0 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.
The data
Island County, At a glance
Island County at a glance
Predicted: EPA radon zone
EPA Zone 3: lower predicted potential
USGS geologic potential: Low across 19% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Island County, 2020
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 0.0% |
| 2015 | 0.0% |
| 2016 | 4.0% |
| 2017 | 7.7% |
| 2018 | 0.0% |
| 2019 | 22.2% |
| 2020 | 0.0% |
2020: 0.0%. Across these years the share ran from 0.0% to 22.2%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
Only 6 tests were reported to CDC for Island County over 2020, and tests are often run on homes being sold or already suspected of a problem: so few describe neither the county nor this house.
Measured: CDC tracking data. Figure above: 2020. Measured data period: 2005 to 2020 (every CDC figure on file).
Island County, Compared
Island County radon figures, compared
Calculated by Radon411CDC's largest figure for Island County rests on 25 tests in 2016, 1 of them at or above 4 pCi/L, so each test moves its share by 4.0 points and no rank or comparison is drawn from it. Results reached as high as 5.7 pCi/L, with a middle value of 1.7 pCi/L.
Snohomish County, the one bordering county with a figure over the 2008 to 2017 laboratory totals, reported 2.3% of its tests at or above 4 pCi/L. Farther out, Kitsap County (38 miles away) at 4.9%, Skagit County (44 miles away) at 2.8% and King County (58 miles away) at 2.6% have figures too. Pooled across 39 Washington counties, 25.5% of reported tests reached that level; across every county in the country with a figure, 35.7%.
Statewide for the same period, Pend Oreille County reported the highest share (63.2%) and Snohomish County the lowest (2.3%). EPA's 1993 map puts Island County in Zone 3, its lowest label: a predicted county average under 2 pCi/L. USGS geology rates 19% of the county's land low radon potential.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Island County, Geology
The ground under Island County
PredictedUSGS's geologic map puts all of Island County's mapped land in one class: low radon potential. 18.7% of it lies in the area the map calls Puget Lowlands, to which USGS gives a radon index of 6, in the low band (5 to 8).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Puget Lowlands | Continental and marine sediments overlain by sandy and silty glacial deposits. | Low | 6 | 18.7% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Island County beside the ground around it
Across Washington 13.7% of the land is rated high; none of Island County's is. None of the one county that borders it has any moderate-potential ground either.
The map rates the ground, not the air in any home.
Local help
Island County, Local resources
Radon testing and mitigation in Island County
- Radon ProgramRadon Program, run by Washington State Department of Health, offers free or discounted test kits, and answers questions about testing and mitigation in Washington.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
We have a limited supply of free radon test kits.
- Compare kits
- See the Washington directoryNo professionals are listed in Washington yet. The state program can point you to registered testers and mitigators.
What Washington's program says
- Phone
- 360-236-3200
- doh.radon@doh.wa.gov
What it means
Island County, Questions
Questions about radon in Island County
Are radon levels high in Island County?
In 2020, 0.0% of the radon tests reported to CDC for Island County, Washington were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.1 pCi/L. Snohomish County, the one bordering county with a figure over the 2008 to 2017 laboratory totals, reported 2.3% of its tests at or above 4 pCi/L.
Which counties border Island County?
Island County borders 1 county: Snohomish County.
Products
Island County, Products
Testing a home in Island County
No CDC figure names Island County; the nearest county with one, Kitsap County (38 miles away), reported 4.9% of its tests at or above 4 pCi/L over the 2008 to 2017 laboratory totals, the only reading nearby until a test of this home. 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 Island 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
Island County, Bordering counties
Counties bordering Island County
Calculated by Radon411- Radon levels in Snohomish CountyEPA zone 3
2.3%at or above 4 pCi/L
Median 0.5 pCi/L · 265 tests
Island County, Cities and towns
Cities and towns in Island County
About 85,657 people live in Island County by the Census Bureau's estimate for July 1, 2025, 1,344 fewer than in 2020 (−1.5%). That works out to 411 people per square mile of land. Its largest town, Oak Harbor, has 24,083 residents, 28.1% of the total. Together its 3 incorporated places hold 31.7% of those residents; the other 68.3% live outside any of them. Reported testing is thin here: 25 tests over 2016, or 0.3 for every 1,000 residents (2025 estimate), where Washington as a whole comes to 0.6.
From Oak Harbor to Langley, CDC publishes no figure by town: each reads Island County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Oak Harbor | 24,083 | −2.2% | 28.1% |
| Coupeville | 1,920 | −1.3% | 2.2% |
| Langley | 1,129 | −1.9% | 1.3% |
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).
Island County, Homes
Homes in Island County
Island County is a place of houses on their own lots: 78% of its 42,398 homes are detached single-family houses, against 62% across Washington. Half of its homes were built before 1990, close to Washington's 1984: 12% date from before 1960 and 26% from 2000 or later. 75% of occupied homes are lived in by their owner (Washington: 64%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Island County | Washington |
|---|---|---|
| Housing units | 42,398 | 3,262,667 |
| Detached houses | 78% | 62% |
| In buildings of 5 or more | 6% | 22% |
| Mobile homes | 7% | 6% |
| Built before 1960 | 12% | 21% |
| Built since 2000 | 26% | 28% |
| Middle year built | 1990 | 1984 |
| Owner-occupied | 75% | 64% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.