Is Weld County, CO a radon risk area?

EPA's own radon map rates Weld County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. That puts Weld County in the 98th percentile nationally for radon potential — higher than 98% of the counties EPA has rated.

Where Weld County sits nationally

About 369,745 people live in Weld County, Colorado, spread over 3,984.963 square miles. Population density there runs about 93 people per square mile. Rank 65 by population within its EPA zone puts Weld County at the 94th percentile among zone peers. Geologically, Weld 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

Where the national indoor average runs about 1.3 pCi/L, Weld County's Zone 1 rating puts its predicted county average above EPA's 4 pCi/L action level itself. EPA's guidance doesn't change because of a Zone 1 label: test the house. What changes is the reason to not put it off in Weld County specifically.

If Weld County tests above the action level

Nothing about Weld 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

Weld County's test kit answers today; a Airthings radon monitor keeps answering for Weld County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. RADONZONE-10OFF at checkout knocks 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. Whatever zone Weld County carries, the zone explainer covers what it does and doesn't tell you about any one house.