St. Tammany Parish, LA: EPA's radon zone, explained

St. Tammany Parish is mapped as Zone 3 - Low Potential by EPA — meaning the county-wide average indoor level is predicted below 2 pCi/L. Nationally that's the 30th percentile for radon potential — St. Tammany Parish outranks 30% of every county EPA has rated.

Where St. Tammany Parish sits nationally

St. Tammany Parish, Louisiana is home to about 277,615 people across 845.308 square miles. That works out to roughly 328 people per square mile. By population, St. Tammany Parish is the 92nd largest of every county sharing its EPA zone — the 91st percentile by population within that zone. Geologically, St. Tammany Parish is grouped into EPA Region 6 alongside 502 other counties that share its rock and soil setting.

What this actually means for a house in St. Tammany Parish

St. Tammany Parish's Zone 3 prediction undercuts the roughly 1.3 pCi/L most US homes average, nowhere near EPA's 4 pCi/L threshold for recommending mitigation. Low doesn't mean zero: EPA's own data shows homes in Zone 3 counties like St. Tammany Parish testing above the action level often enough that skipping a test isn't the safe assumption.

Next steps for a home in St. Tammany Parish

For a St. Tammany Parish 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 Louisiana's state radon program

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

Where St. Tammany Parish's figures come from

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