Summit County, CO: EPA's radon zone, explained

EPA's own radon map rates Summit County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. Nationally that's the 85th percentile for radon potential — Summit County outranks 85% of every county EPA has rated.

Where Summit County sits nationally

Summit County, Colorado is home to about 30,882 people across 608.328 square miles. Population density there runs about 51 people per square mile. By population, Summit County is the 459th largest of every county sharing its EPA zone — the 57th percentile by population within that zone. Summit 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

Where the national indoor average runs about 1.3 pCi/L, Summit 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 Summit County specifically.

Next steps for a home in Summit County

For a Summit County homeowner, the order is simple: test first, since a kit costs a small fraction of what mitigation would. Only if the result clears 4 pCi/L does a system — typically $800–$2,500, about $1,200 for a common install — become worth pricing out.

Find Colorado's state radon program

For Summit County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Summit County's levels over time. RadonZoneCheck earns a commission there, at no extra cost to you. Code RADONZONE-10OFF takes 10% off at checkout.

Where Summit County's figures come from

The methodology guide shows exactly which EPA and Census sources feed Summit County's numbers. Whatever zone Summit County carries, the zone explainer covers what it does and doesn't tell you about any one house.