Cassia County, ID: EPA's radon zone, explained

EPA places Cassia County in Zone 2 - Moderate Potential — a predicted county-wide average indoor radon level between 2 and 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Cassia County sits at the 49th percentile nationally for radon potential — above 49 of every 100 rated counties.

Where Cassia County sits nationally

Cassia County, Idaho is home to about 25,976 people across 2,565.61 square miles. Population density there runs about 10 people per square mile. By population, Cassia County is the 541st largest of every county sharing its EPA zone — the 48th percentile by population within that zone. Cassia County falls in EPA Radon Region 10, one of 142 counties nationally EPA assigns to that same geologic province.

Zone vs. an actual test

Cassia County's Zone 2 prediction clears the 1.3 pCi/L national indoor average without reaching EPA's own 4 pCi/L point for recommending a fix. A county-wide moderate average, like Cassia County's, can still hide a specific house well above or below it — testing is what actually answers the question.

If Cassia County tests above the action level

For a Cassia 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 Idaho's state radon program

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

Cassia County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.