Radon testing in Spokane: what it costs, and why Spokane County is EPA Zone 1

Why Spokane specifically

Radon is a colorless, odorless radioactive gas that comes up out of the ground and collects inside buildings.

The zone. The EPA places Spokane County in Zone 1, the highest of its three radon potential zones, where average indoor radon levels may be greater than 4 pCi/L.
The way houses here are built and lived in. Finished basements are normal in Spokane, and the basement is exactly where radon collects. Then winter closes the house for months, at the same time of year the basement gets used most.

None of that means your house has a problem. It means you cannot know without testing. Two houses on the same street can test very differently, so a neighbor's result does not tell you yours.

The number that matters is 4.0 pCi/L. That is the EPA action level. At or above it, mitigation is recommended. Between 2.0 and 4.0 the EPA suggests considering it. The EPA says "any radon exposure carries some risk" (A Citizen's Guide to Radon), but 4.0 is where the decision gets straightforward.

What this site covers

Testing

Short term charcoal tests, long term detectors, and continuous monitors. Which one you need depends on whether you are selling a house or living in it.

How testing works →

Mitigation

If your result comes back high, a sub slab depressurization system vents the gas outside before it enters the house.

How mitigation works →

Reading your result

A number by itself does not tell you much. Where the test sat, how long, and whether the house was closed all change it.

Understanding levels →

Buying or selling

Radon comes up constantly in Spokane real estate transactions, and the timeline is tight. There are rules about who tests and how.

Real estate testing →

The mistake that costs people money

Buying a cheap hardware store kit, running it with the windows open in July, getting a low number, and concluding the house is fine. For short-term tests of two to three days, the EPA's Citizen's Guide calls for closed house conditions: windows and exterior doors shut except for normal entry and exit, for at least twelve hours before the test starts and the whole time it runs.

Run the same test the same way in January with the house sealed against a Spokane winter and the number can be higher. That is not the test being wrong. That is the test finally measuring the conditions you actually live in.

Where the facts come from

EPA, A Citizen's Guide to Radon (2016) (Federal), checked Nov 2, 2026
EPA, Map of Radon Zones (Federal), checked Nov 2, 2026