What EPA's radon map says about Nassau County

Nassau County is mapped as Zone 3 - Low Potential by EPA — meaning the county-wide average indoor level is predicted below 2 pCi/L. That puts Nassau County in the 32nd percentile nationally for radon potential — higher than 32% of the counties EPA has rated.

Where Nassau County sits nationally

About 1,392,438 people live in Nassau County, New York, spread over 284.544 square miles. Averaged across its land area, Nassau County runs about 4,894 people per square mile. Among counties sharing Nassau County's EPA zone, it outranks 98% of them by population. Nassau County falls in EPA Radon Region 2, one of 83 counties nationally EPA assigns to that same geologic province.

What this actually means for a house in Nassau County

At Zone 3, Nassau County's predicted county average is under the national indoor average (~1.3 pCi/L) and well below EPA's 4 pCi/L action level — outdoor air nationally runs about 0.4 pCi/L for comparison. Low doesn't mean zero: EPA's own data shows homes in Zone 3 counties like Nassau County testing above the action level often enough that skipping a test isn't the safe assumption.

Testing and mitigation in Nassau County

Mitigation cost doesn't depend on Nassau 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 New York's state radon program

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

More on how this number was built

Nassau County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.