Radon in ZIP code 99033
Last updated
ZIP 99033 crosses 3 county lines. Most of its land (82%) is in Whitman County, Washington. EPA’s radon zone for this area: Zone 1, highest potential.
Predicted average indoor screening level from 2 to 4 pCi/L.
Predicted average indoor screening level above 4 pCi/L.
Predicted average indoor screening level above 4 pCi/L.
What this means for homes in 99033
EPA built its zone map county by county in 1993, so every address in each part of 99033 shares its county’s prediction. The zone is a starting point, not a measurement of your house. Zone 1 areas like this one have a high share of homes above 4 pCi/L, so testing is a priority.
Because 99033 crosses county lines, your county depends on your street. Your property tax bill or county assessor site shows which county you are in. Next: read how to test your home, then check the number with the level calculator.
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Nearby ZIP codes in Whitman County
Washington radon help
WA State Department of Health, Community and Environment: Radon (360-236-3200) can help with test kits, local data and credentialed professionals: doh.wa.gov/community-and-environment/contaminants/radon.
Frequently asked questions
What is the radon zone for ZIP code 99033?
ZIP 99033 spans 3 counties. The highest-potential zone among them is Zone 1 (highest potential). Whitman County: Zone 2 (82% of the ZIP's land); Spokane County: Zone 1 (16.1% of the ZIP's land); Benewah County: Zone 1 (1.9% of the ZIP's land).
Should I test for radon in 99033?
Yes. EPA recommends testing every home regardless of zone, because radon varies from house to house. Fix the home if a confirmed result is 4 pCi/L or higher, and consider fixing between 2 and 4 pCi/L.
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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