Martin County, FL: EPA's radon zone, explained

Martin County is mapped as Zone 3 - Low Potential by EPA — meaning the county-wide average indoor level is predicted below 2 pCi/L. Rank it against the rest of the country and Martin County lands in the 28th percentile for radon potential.

Where Martin County sits nationally

Martin County, Florida is home to about 165,666 people across 543.873 square miles. Population density there runs about 305 people per square mile. By population, Martin County is the 157th largest of every county sharing its EPA zone — the 85th percentile by population within that zone. Geologically, Martin County is grouped into EPA Region 4 alongside 735 other counties that share its rock and soil setting.

What this actually means for a house in Martin County

Martin County's predicted average sits below the national indoor average of about 1.3 pCi/L, well under EPA's 4 pCi/L action level. A Zone 3 label describes Martin County's average, not any one basement or slab in it — testing is still the only way an individual homeowner actually finds out.

Next steps for a home in Martin County

For a Martin 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 Florida's state radon program

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

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