Is Grand County, CO a radon risk area?

EPA's own radon map rates Grand County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. Nationally that's the 80th percentile for radon potential — Grand County outranks 80% of every county EPA has rated.

Where Grand County sits nationally

About 16,154 people live in Grand County, Colorado, spread over 1,846.582 square miles. Population density there runs about 9 people per square mile. Rank 639 by population within its EPA zone puts Grand County at the 40th percentile among zone peers. Geologically, Grand County is grouped into EPA Region 8 alongside 290 other counties that share its rock and soil setting.

Why the zone isn't the answer by itself

Outdoor air nationally averages about 0.4 pCi/L, indoor air about 1.3 pCi/L — Grand County's Zone 1 prediction clears both of those and EPA's fix-it threshold besides. That doesn't mean every Grand County house tests high — a zone is a county-wide prediction, never a single-home reading — but it's a reason to test sooner rather than let it wait.

Next steps for a home in Grand County

Nothing about Grand 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 Colorado's state radon program

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

More on how this number was built

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.