Clay County, IA radon potential

EPA places Clay County in Zone 1 - Highest Potential — a predicted county-wide average indoor radon level above 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Clay County sits at the 80th percentile nationally for radon potential — above 80 of every 100 rated counties.

Where Clay County sits nationally

Clay County, Iowa is home to about 16,474 people across 567.238 square miles. That works out to roughly 29 people per square mile. Within its own EPA zone, Clay County is bigger by population than 41% of the counties that share it. Geologically, Clay County is grouped into EPA Region 7 alongside 411 other counties that share its rock and soil setting.

What this actually means for a house in Clay County

Clay 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. EPA's guidance doesn't change because of a Zone 1 label: test the house. What changes is the reason to not put it off in Clay County specifically.

Next steps for a home in Clay County

A short-term test kit is the standard first step and typically costs far less than mitigation itself. If a test comes back at or above 4 pCi/L, a radon mitigation system for a typical home runs roughly $800–$2,500 (around $1,200 for a common single-family install), driven mainly by foundation type, not by county.

Find Iowa's state radon program

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

The methodology guide shows exactly which EPA and Census sources feed Clay County's numbers. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.