Is Fremont County, ID a radon risk area?

Fremont County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Rank it against the rest of the country and Fremont County lands in the 78th percentile for radon potential.

How Fremont County compares

About 14,399 people live in Fremont County, Idaho, spread over 1,863.96 square miles. That works out to roughly 8 people per square mile. Rank 674 by population within its EPA zone puts Fremont County at the 37th percentile among zone peers. Geologically, Fremont County is grouped into EPA Region 10 alongside 141 other counties that share its rock and soil setting.

Why the zone isn't the answer by itself

Fremont County's predicted average sits above EPA's own action level of 4 pCi/L — the concentration at which EPA recommends fixing a home — versus a national average around 1.3 pCi/L indoors and 0.4 pCi/L outdoors. Being in Zone 1 raises the odds Fremont County homes test above the action level, but it does not mean any specific house does — EPA recommends every home be tested, in every zone, because the only way to know is to test.

Next steps for a home in Fremont County

Nothing about Fremont County's EPA zone changes the mitigation number: $800–$2,500 nationally (around $1,200 typical), set by the house's foundation rather than the county it sits in — and only relevant once a test actually clears 4 pCi/L.

Find Idaho's state radon program

Fremont County's test kit answers today; a Airthings radon monitor keeps answering for Fremont County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. Code RADONZONE-10OFF takes 10% off at checkout.

More on how this number was built

The methodology guide shows exactly which EPA and Census sources feed Fremont County's numbers. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.