Coconino County, AZ: EPA's radon zone, explained

Coconino County is mapped as Zone 2 - Moderate Potential by EPA — meaning the county-wide average indoor level is predicted between 2 and 4 pCi/L. Coconino County sits at the 61st percentile nationally for radon potential — above 61 of every 100 rated counties.

Where Coconino County sits nationally

Coconino County, Arizona is home to about 145,161 people across 18,616.366 square miles. That works out to roughly 8 people per square mile. By population, Coconino County is the 153rd largest of every county sharing its EPA zone — the 85th percentile by population within that zone. Coconino County falls in EPA Radon Region 9, one of 95 counties nationally EPA assigns to that same geologic province.

Why the zone isn't the answer by itself

Neither at the 4 pCi/L action level nor down at the roughly 1.3 pCi/L national indoor norm, Coconino County's Zone 2 prediction lands in the gap between the two. Middle-of-the-pack doesn't mean risk-free for any one Coconino County address — a moderate county average still leaves individual homes to test either side of it.

Testing and mitigation in Coconino County

For a Coconino 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 Arizona's state radon program

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

Where Coconino 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. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.