Dallas County, IA: EPA's radon zone, explained

EPA's own radon map rates Dallas County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. Dallas County sits at the 95th percentile nationally for radon potential — above 95 of every 100 rated counties.

Dallas County by the numbers

Dallas County, Iowa is home to about 115,343 people across 588.23 square miles. Averaged across its land area, Dallas County runs about 196 people per square mile. By population, Dallas County is the 168th largest of every county sharing its EPA zone — the 84th percentile by population within that zone. Geologically, Dallas 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 Dallas County

Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line Dallas County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. Some Dallas County homes will test comfortably under the action level despite the county's Zone 1 rating — the only way to know which kind of home you have is an actual test.

If Dallas County tests above the action level

For a Dallas 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 Iowa's state radon program

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

Where Dallas County's figures come from

The methodology guide shows exactly which EPA and Census sources feed Dallas County's numbers. Whatever zone Dallas County carries, the zone explainer covers what it does and doesn't tell you about any one house.