Short-term kit
PicoCan short-term charcoal canister radon test
- Lab fee included
Method: Charcoal
In home: 48 to 96 hours
Locations and reports
Radon Levels in Thurston County, Washington
EPA puts Thurston County in Zone 3, its lowest radon zone, and most reported tests there come back low, though 6.5% of 46 (2020) 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
6.5%
12.5 pts below WA
- Thurston
- 6.5%
- Washington
- 19.0%
46 tests, 2020
Median result
0.4pCi/L
Below action level
- Thurston
- 0.4 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2020
Tests reported
46
8th of 10 by tests
- Thurston
- 46
- Spokane
- 721
Reported to CDC before any fix, 2020
EPA radon zone
Zone 3
Lower potential
- 1
- 2
- Zone 3
1 highest, 3 lowest
EPA predicts under 2 pCi/L indoors
Rank in Washington
5 of 10
Middle half
- Thurston
- 6.5%
- Spokane
- 40.6%
By share, of 10 with 30+ tests
Read a result for Thurston County
Starts at Thurston County's median, 0.4 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 0.4 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. Thurston County's median reported result, 2020.
The data
Thurston County, At a glance
Thurston County at a glance
Predicted: EPA radon zone
EPA Zone 3: lower predicted potential
USGS geologic potential: Low across 97% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Thurston County, 2020
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 6.3% |
| 2015 | 7.5% |
| 2016 | 23.1% |
| 2017 | 8.6% |
| 2018 | 0.0% |
| 2019 | 30.2% |
| 2020 | 6.5% |
2020: 6.5%. Across these years the share ran from 0.0% to 30.2%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
These are the 46 tests reported to CDC for Thurston County over 2020, 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: 2020. Measured data period: 2005 to 2020 (every CDC figure on file).
Thurston County, Compared
Thurston County radon figures, compared
Calculated by Radon411Thurston County reports fewer high tests than Washington overall. 6.5% of its 46 tests in 2020 were at or above 4 pCi/L. That is 12.5 points below the 19.0% pooled from 37 Washington counties.
Ordered from highest share down, it comes 5th of 10 Washington counties with 30 or more tests for the same period. Nationally, every county with a figure for the same period pools to 25.5%; Thurston County sits 19.0 points below it.
Pierce County, the one bordering county with a figure for the same period, reported 4.3%. Zone 3 on EPA's map (predicted average under 2 pCi/L) and a 6.5% share point the same way here.
Half the tests came in under 0.4 pCi/L and half over it; the single highest reached 7.4 pCi/L. The rest split 78.3% under 2 pCi/L and 15.2% from 2 to 4 (Washington: 67.6% and 13.3%). Year by year, 2014 opened at 6.3% and 2020 closed at 6.5% (about level), with 2019 the high at 30.2%.
The busiest year on file was 2014, with 112 tests reported; the quietest, 2016, had 26.
Thurston CountyWashington, pooled
6.5% % of tests19.0% % of tests
| Year | Tests | Thurston County, at or above 4 pCi/L | Washington, pooled |
|---|---|---|---|
| 2014 | 112 | 6.3% | 15.0% |
| 2015 | 67 | 7.5% | 17.4% |
| 2017 | 58 | 8.6% | 19.1% |
| 2018 | 60 | 0.0% | 16.1% |
| 2019 | 63 | 30.2% | 20.9% |
| 2020 | 46 | 6.5% | 19.0% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
Thurston County, Geology
The ground under Thurston County
PredictedUSGS's geologic map puts all of Thurston County's mapped land in one class: low radon potential. The map puts 58.8% of Thurston County in the area it calls Puget Lowlands and 21.6% in Cascade Mountains, with one smaller area beside them. USGS gives both 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 | 58.8% |
| Cascade Mountains | Northern Cascade Mountains are Mesozoic metamorphic rocks intruded by Mesozoic and Tertiary granitic rocks. Southern Cascade Mountains are composed primarily of Tertiary and Holocene volcanic rocks. | Low | 6 | 21.6% |
| Coastal Hills | Cretaceous and Tertiary continental and marine sedimentary rocks and pre-Miocene volcanic rocks. | Low | 6 | 16.4% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Thurston County beside the ground around it
Across Washington 13.7% of the land is rated high; none of Thurston County's is. None of the 4 counties that border it has any moderate-potential ground either.
The map rates the ground, not the air in any home.
Local help
Thurston County, Local resources
Radon testing and mitigation in Thurston 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
Thurston County, Questions
Questions about radon in Thurston County
Are radon levels high in Thurston County?
In 2020, 6.5% of the radon tests reported to CDC for Thurston County, Washington were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.4 pCi/L. Of 10 Washington counties with 30 or more tests for the same period, 4 reported a higher share; pooled, the state comes to 19.0%.
Which counties border Thurston County?
Thurston County borders 4 counties: Mason County, Lewis County, Pierce County and Grays Harbor County.
Products
Thurston County, Products
Testing a home in Thurston County
In Thurston County, 6.5% of 46 tests reported to CDC in 2020 reached 4 pCi/L, against 19.0% pooled across Washington. 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 Thurston 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
Monitor
RadonScan-Plus USB-powered radon monitor with Wi-Fi
- C-NRPP 2024/25: Not included
- Plug-in
- Wi-Fi
- Alarm
- Screen, app
First reading: Within 5 minutes
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Thurston County, Bordering counties
Counties bordering Thurston County
Calculated by Radon411- Radon levels in Lewis CountyEPA zone 3
70.0%at or above 4 pCi/L
Median 15.6 pCi/L · 10 tests · 63.5 points above Thurston County
- Radon levels in Pierce CountyEPA zone 3
4.3%at or above 4 pCi/L
Median 0.7 pCi/L · 420 tests · 2.2 points below Thurston County
- Radon levels in Mason CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 1.7 pCi/L · 3 tests · 6.5 points below Thurston County
- Radon levels in Grays Harbor CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 1.3 pCi/L · 9 tests · 6.5 points below Thurston County
Thurston County, Cities and towns
Cities and towns in Thurston County
The Census Bureau estimates 304,261 residents in Thurston County for July 1, 2025, 8,248 more than in 2020 (+2.8%). That works out to 421 people per square mile of land. No town dominates: Lacey, the largest, has 58,833 residents, 19.3% of the total. Together its 7 incorporated places hold 52.8% of those residents; the other 47.2% live outside any of them. Reported testing is thin here: 46 tests over 2020, or 0.2 for every 1,000 residents (2025 estimate), where Washington as a whole comes to 0.3.
From Lacey to Bucoda, CDC publishes no figure by town: each reads Thurston County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Lacey | 58,833 | +3.6% | 19.3% |
| Olympia | 56,724 | +2.0% | 18.6% |
| Tumwater | 28,010 | +7.2% | 9.2% |
| Yelm | 12,043 | +12.6% | 4.0% |
| Rainier | 2,495 | +4.7% | 0.8% |
| Tenino | 1,941 | +3.6% | 0.6% |
| Bucoda | 630 | +5.4% | 0.2% |
7 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).
Thurston County, Homes
Homes in Thurston County
Of Thurston County's 123,333 homes, 67% are detached houses, against 62% across Washington; 14% are in buildings of five or more homes. Half of its homes were built before 1991, close to Washington's 1984: 11% date from before 1960 and 33% from 2000 or later. 68% 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 | Thurston County | Washington |
|---|---|---|
| Housing units | 123,333 | 3,262,667 |
| Detached houses | 67% | 62% |
| In buildings of 5 or more | 14% | 22% |
| Mobile homes | 9% | 6% |
| Built before 1960 | 11% | 21% |
| Built since 2000 | 33% | 28% |
| Middle year built | 1991 | 1984 |
| Owner-occupied | 68% | 64% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.