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

EPA places Sac 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. Nationally, Sac County ranks higher in radon potential than 75% of rated counties (the 75th percentile).

How Sac County compares

Sac County, Iowa is home to about 9,533 people across 575.022 square miles. Averaged across its land area, Sac County runs about 17 people per square mile. By population, Sac County is the 777th largest of every county sharing its EPA zone — the 27th percentile by population within that zone. Geologically, Sac County is grouped into EPA Region 7 alongside 411 other counties that share its rock and soil setting.

Zone vs. an actual test

Where the national indoor average runs about 1.3 pCi/L, Sac County's Zone 1 rating puts its predicted county average above EPA's 4 pCi/L action level itself. Being in Zone 1 raises the odds Sac 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 Sac County

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

Where Sac County's figures come from

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