Washington Radon Map, Levels & Testing Guide
Browse the 4 listed county pages surfaced for Washington. Open a listed county to compare its EPA zone, source caveats, testing meaning, and when mitigation pricing becomes worth checking.
High Risk
Moderate
Low Risk
Official Evidence in Washington
4 of 4 listed counties have official evidence
Open a county page to see the official source context: measurement fields, local burden, state percentile, and the next step for no reading, 2.0-3.9, or 4.0+ pCi/L.
100%
covered
Measured
4
State source
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CDC source
4
Needs source detail
0
Measured Risk Leaders in Washington
County rankings from actual reported radon tests
These lists rank the visible Washington county pages by measured radon signals, not by the EPA zone label alone. Use them to spot where the state hub has a real data story before opening individual county pages.
4
measured counties
State-level evidence read
This hub has measured high-burden counties, so the first click should be evidence-led.
The state hub is now doing a decision job: it separates first-click counties, retest counties, and lower-signal counties from 4 visible county measurement rows. 1 counties cross the high measured-burden band, so those pages should answer testing and 4.0+ action questions most directly.
First-click counties
Open Spokane County first when you need the strongest local answer. It is tagged Test-now from 41.4% 4.0+ - 6.6 pCi/L primary - 2,249 tests. 2 visible measured counties are elevated or high enough to review before lower-signal counties.
Buyer/seller lane
Buyer/seller lane: start with the elevated or high counties, require a fresh lowest-level test, and turn any 4.0+ property result into quote or credit math. The hub has 4 CDC-backed county rows to support that routing.
Retest lane
Retest lane: 2.0-3.9 pCi/L deserves more caution in the elevated/high county set than in lower-signal counties. The hub should send those users to county pages before product or cost paths.
Best county pages to open first
Start with these local evidence pages
Ranked by measured burden, 4.0+ share, test volume, and whether the EPA zone understates the measurement signal.
Spokane County
CDC Tracking
41.4% 4.0+ - 6.6 pCi/L primary - 2,249 tests
Spokane County is a first-click page: 41.4% of reported tests at or above 4.0 and 6.6 pCi/L primary result. Route no-reading users to a test now and 4.0+ users to quote or credit planning.
Clark County
CDC Tracking
25.1% 4.0+ - 3.5 pCi/L primary - 1,265 tests
Clark County should be opened before lower-signal counties: 25.1% of reported tests at or above 4.0 and 3.5 pCi/L primary result. It is strong enough for testing and retesting language on the hub.
Whitman County
CDC Tracking
22.4% 4.0+ - 2.9 pCi/L primary - 41 tests
Whitman County belongs in the retest lane: 22.4% of reported tests at or above 4.0 and 2.9 pCi/L primary result. A 2.0-3.9 home result should be confirmed before the user dismisses it.
San Juan County
CDC Tracking
0.0% 4.0+ - 0.7 pCi/L primary - 8 tests
San Juan County is lower at county level: 0.0% of reported tests at or above 4.0 and 0.7 pCi/L primary result. Keep the page home-specific rather than presenting it as a statewide alarm.
Highest 4.0+ share
Primary result 6.6 pCi/L - high-end 178.5 pCi/L
CDC Tracking
Primary result 3.5 pCi/L - high-end 75.8 pCi/L
CDC Tracking
Primary result 2.9 pCi/L - high-end 19.0 pCi/L
CDC Tracking
Primary result 0.7 pCi/L - high-end 2.1 pCi/L
CDC Tracking
Highest high-end reading
4.0+ share 41.4% - primary result 6.6 pCi/L
CDC Tracking
4.0+ share 25.1% - primary result 3.5 pCi/L
CDC Tracking
4.0+ share 22.4% - primary result 2.9 pCi/L
CDC Tracking
4.0+ share 0.0% - primary result 0.7 pCi/L
CDC Tracking
Most reported tests
4.0+ share 41.4% - primary result 6.6 pCi/L
CDC Tracking
4.0+ share 25.1% - primary result 3.5 pCi/L
CDC Tracking
4.0+ share 22.4% - primary result 2.9 pCi/L
CDC Tracking
4.0+ share 0.0% - primary result 0.7 pCi/L
CDC Tracking
Measured pattern
Among 4 visible counties with measurement tables, 1 land in the high measured-burden band and 2 land in high or elevated measured-burden bands. That lets this hub rank counties by observed test distribution instead of repeating the EPA map.
Map vs measurements
The strongest measured signals mostly align with the EPA zone structure, so the county pages can use the map as support while still leading with test data.
Source strategy
The measured rows shown here use CDC Tracking. This is still official evidence, but the hub should keep source caveats visible until a stable state table is available.
Already Tested
View Washington Cost Estimates
If you already have a radon result, skip the directory and move straight to local price guidance.
Understand the Number
2.0 vs 4.0 vs 8.0 pCi/L
Use the parent levels guide if you need the plain-English meaning of a radon result before browsing counties.
Need a Number First
Read the Testing Guide
Use the fastest valid radon test setup before you compare quotes or ask whether mitigation is worth it.
Browse Counties
Jump to the Directory
Open your county to see its EPA zone, testing meaning, and the point where mitigation becomes worth pricing.
Official State Resource
Washington radon program and rules
Use the state program link to verify local radon guidance, disclosure language, and contractor credential expectations before you act on an estimate.
Disclosure rule tracked
Washington requires sellers to complete a Seller Disclosure Statement (Form 17) covering environmental hazards.
Credential note
Washington does not require specific radon licensing.
Already tested? Get your itemized mitigation cost estimate.
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