What EPA's radon map says about Adams County

EPA places Adams County in Zone 1 - Highest Potential — a predicted county-wide average indoor radon level above 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. That puts Adams County in the 99th percentile nationally for radon potential — higher than 99% of the counties EPA has rated.

Adams County by the numbers

About 542,973 people live in Adams County, Colorado, spread over 1,166.8 square miles. Population density there runs about 465 people per square mile. Among counties sharing Adams County's EPA zone, it outranks 97% of them by population. Adams County falls in EPA Radon Region 8, one of 291 counties nationally EPA assigns to that same geologic province.

Why the zone isn't the answer by itself

Adams County carries a Zone 1 label because its predicted average clears 4 pCi/L outright — three-plus times the 0.4 pCi/L typical outdoors and above the 1.3 pCi/L most homes see. 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 Adams County specifically.

Next steps for a home in Adams County

Mitigation cost doesn't depend on Adams County's zone — it depends on the house's foundation. A typical system runs $800–$2,500 (about $1,200 typical), and testing first is what tells you whether that's needed at all.

Find Colorado's state radon program

Adams County's test kit answers today; a Airthings radon monitor keeps answering for Adams 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

Adams County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.