San Juan County, CO: EPA's radon zone, explained

EPA's own radon map rates San Juan County zone 2 - moderate potential, predicting a county-wide average indoor level between 2 and 4 pCi/L. San Juan County sits at the 33rd percentile nationally for radon potential — above 33 of every 100 rated counties.

How San Juan County compares

San Juan County, Colorado is home to about 821 people across 387.516 square miles. Averaged across its land area, San Juan County runs about 2 people per square mile. By population, San Juan County is the 1024th largest of every county sharing its EPA zone — the 1st percentile by population within that zone. San Juan County falls in EPA Radon Region 8, one of 291 counties nationally EPA assigns to that same geologic province.

Zone vs. an actual test

Call it a middle case: above the 1.3 pCi/L most US homes average, below the 4 pCi/L line EPA uses to recommend mitigation — that's San Juan County's Zone 2 prediction. Nothing about a Zone 2 label lowers the case for testing in San Juan County — EPA recommends it in every zone, moderate included.

Testing and mitigation in San Juan County

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

The methodology guide shows exactly which EPA and Census sources feed San Juan County's numbers. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.