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

Fremont County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Nationally that's the 90th percentile for radon potential — Fremont County outranks 90% of every county EPA has rated.

Fremont County by the numbers

Fremont County, Colorado is home to about 50,093 people across 1,533.835 square miles. Population density there runs about 33 people per square mile. By population, Fremont County is the 312th largest of every county sharing its EPA zone — the 71st percentile by population within that zone. Fremont 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

Outdoor air nationally averages about 0.4 pCi/L, indoor air about 1.3 pCi/L — Fremont County's Zone 1 prediction clears both of those and EPA's fix-it threshold besides. Some Fremont County homes will test comfortably under the action level despite the county's Zone 1 rating — the only way to know which kind of home you have is an actual test.

Testing and mitigation in Fremont County

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

Where Fremont County's figures come from

Fremont County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. Whatever zone Fremont County carries, the zone explainer covers what it does and doesn't tell you about any one house.