Grand County, UT: EPA's radon zone, explained

Grand County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Nationally, Grand County ranks higher in radon potential than 75% of rated counties (the 75th percentile).

How Grand County compares

Grand County, Utah is home to about 9,788 people across 3,672.858 square miles. Population density there runs about 3 people per square mile. By population, Grand County is the 771st largest of every county sharing its EPA zone — the 28th percentile by population within that zone. EPA's geology-based Region 8 groups Grand County with 290 other counties nationally sharing its underlying rock and soil profile.

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 — Grand County's Zone 1 prediction clears both of those and EPA's fix-it threshold besides. Being in Zone 1 raises the odds Grand 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.

Next steps for a home in Grand County

For a Grand 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 Utah's state radon program

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

Where Grand County's figures come from

Grand County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.