What EPA's radon map says about Gwinnett County

EPA places Gwinnett 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. Gwinnett County sits at the 100th percentile nationally for radon potential — above 100 of every 100 rated counties.

Where Gwinnett County sits nationally

About 1,003,869 people live in Gwinnett County, Georgia, spread over 431.135 square miles. Population density there runs about 2,328 people per square mile. Among counties sharing Gwinnett County's EPA zone, it outranks 99% of them by population. EPA's geology-based Region 4 groups Gwinnett County with 735 other counties nationally sharing its underlying rock and soil profile.

Zone vs. an actual test

Gwinnett County's predicted average sits above EPA's own action level of 4 pCi/L — the concentration at which EPA recommends fixing a home — versus a national average around 1.3 pCi/L indoors and 0.4 pCi/L outdoors. 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 Gwinnett County specifically.

Testing and mitigation in Gwinnett County

Mitigation cost doesn't depend on Gwinnett County's zone — it depends on the house's foundation. A typical system runs $800–$2,500 (about $1,200 typical), and testing first is what tells you whether that's needed at all.

Find Georgia's state radon program

Gwinnett County's test kit answers today; a Airthings radon monitor keeps answering for Gwinnett County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. Use code RADONZONE-10OFF at checkout for 10% off.

More on how this number was built

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