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

Lake County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Nationally, Lake County ranks higher in radon potential than 73% of rated counties (the 73rd percentile).

How Lake County compares

Lake County, Colorado is home to about 7,369 people across 376.919 square miles. Population density there runs about 20 people per square mile. By population, Lake County is the 836th largest of every county sharing its EPA zone — the 22nd percentile by population within that zone. EPA's geology-based Region 8 groups Lake County with 290 other counties nationally sharing its underlying rock and soil profile.

Why the zone isn't the answer by itself

Lake County's predicted average sits above EPA's own action level of 4 pCi/L — the concentration at which EPA recommends fixing a home — versus a national average around 1.3 pCi/L indoors and 0.4 pCi/L outdoors. That doesn't mean every Lake 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.

Testing and mitigation in Lake County

For a Lake 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 Lake County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Lake 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 Lake County's figures come from

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. Whatever zone Lake County carries, the zone explainer covers what it does and doesn't tell you about any one house.