Carbon County, WY: EPA's radon zone, explained
EPA's own radon map rates Carbon County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. That puts Carbon County in the 78th percentile nationally for radon potential — higher than 78% of the counties EPA has rated.
Carbon County by the numbers
Carbon County, Wyoming is home to about 14,250 people across 7,897.746 square miles. Averaged across its land area, Carbon County runs about 2 people per square mile. By population, Carbon County is the 681st largest of every county sharing its EPA zone — the 36th percentile by population within that zone. Geologically, Carbon County is grouped into EPA Region 8 alongside 290 other counties that share its rock and soil setting.
What this actually means for a house in Carbon County
Carbon 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. Being in Zone 1 raises the odds Carbon County homes test above the action level, but it does not mean any specific house does — EPA recommends every home be tested, in every zone, because the only way to know is to test.
If Carbon County tests above the action level
For a Carbon 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 Wyoming's state radon program
For Carbon County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Carbon 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 Carbon County's figures come from
The methodology guide shows exactly which EPA and Census sources feed Carbon County's numbers. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.