Radon in Clark County, Washington
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Clark County is one of 7 Washington counties (out of 39) that EPA places in Zone 1. 20 ZIP codes reach into the county, 17 of them entirely.
What the zone means for a Clark County home
Zone 1 means EPA predicted an average indoor screening level above 4 pCi/L for Clark County as a whole, the level at which EPA says to fix a home. High readings are common here, so a test is especially worthwhile, and new homes in Clark County are good candidates for radon-resistant construction.
A short-term test kit costs little and takes two to seven days. If your result is 4 pCi/L or higher, EPA recommends a follow-up test and, if it is confirmed, a mitigation system, which typically uses a pipe and fan to pull soil gas from under the foundation and vent it above the roof. Check a result with the level calculator and plan your next step with the follow-up planner.
Finding a radon professional in Clark County
We have not added Washington professionals yet. Until we do, use the Washington radon program (WA State Department of Health, Community and Environment: Radon, 360-236-3200) at doh.wa.gov/community-and-environment/contaminants/radon, or the national certification boards: the NRPP pro search and NRSB find a pro. Or ask for free quotes below.
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Get radon quotes from certified pros in Clark County
Tell us what you need and we will try to connect you with up to three state-certified or licensed radon professionals who work in your area. It is free and there is no obligation.
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ZIP codes in Clark County
Open a ZIP to see every county it touches. Where a ZIP crosses a county line, the percentage is the share of its land area inside Clark County.
Washington radon program
EPA lists WA State Department of Health, Community and Environment: Radon (phone 360-236-3200) as the state contact. State programs can tell you about local test results, discounted kits, disclosure rules for home sales and credentialed professionals. Website: doh.wa.gov/community-and-environment/contaminants/radon.
Back to all Washington counties.
Frequently asked questions
What is the EPA radon zone for Clark County, Washington?
EPA's Map of Radon Zones puts Clark County in Zone 1 (highest potential): Predicted average indoor screening level above 4 pCi/L.
Do I need to test for radon in Clark County if the zone is low?
Yes. EPA says the zone map should not be used to decide whether a single home needs testing. Homes with high radon are found in every zone, and neighboring homes can test very differently. Testing is cheap and the only way to know your level.
How do I find a certified radon professional in Clark County?
Ask the Washington radon program (WA State Department of Health, Community and Environment: Radon, 360-236-3200) for its list of credentialed professionals, or search the national certification boards, NRPP and NRSB. You can also ask for free quotes with the form on this page.
How many ZIP codes are in Clark County?
20 ZIP codes have at least part of their land area in Clark County, based on the U.S. Census Bureau's 2020 ZIP Code Tabulation Area to county relationship file.
Free checklist · PDF
Radon Test Checklist
A one-page, step-by-step checklist for running a home radon test right the first time, and what to do with the number.
- Short-term vs. long-term test: which to use
- Closed-house conditions and where to place the kit
- What 2, 4 and 8 pCi/L mean and when to fix
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