Where it comes from
Radon forms when uranium in soil and rock breaks down. In much of Iowa, the glacial soils hold enough of it that the gas collects under houses.
The EPA lists Linn County among the higher-risk areas, so testing is worth doing here.
How a house pulls it in
A heated house is slightly lower in pressure than the soil around it, especially in winter. That pulls soil air up through cracks, gaps and open sumps.
It is why the lowest level usually reads highest.
How to test
A short-term test runs for a few days in the lowest lived-in room, with the house kept closed up. A longer test shows how levels change through the seasons.
Keep the test away from drafts, windows and the laundry.
What the result means
The EPA recommends fixing a house when the result is 4 pCi/L or higher, and says to consider it when the result is between 2 and 4. Source: US EPA, A Citizen's Guide to Radon.
A low result is good news. Retest after any major change to the house.
What a fix looks like
Most fixes are a pipe, a fan and sealed gaps. They are usually finished in a day.
A follow-up test confirms the result.
