Sullivan County, NY: EPA's radon zone, explained

EPA places Sullivan 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, Sullivan County ranks higher in radon potential than 93% of rated counties (the 93rd percentile).

Where Sullivan County sits nationally

Sullivan County, New York is home to about 80,450 people across 968.145 square miles. Population density there runs about 83 people per square mile. By population, Sullivan County is the 227th largest of every county sharing its EPA zone — the 79th percentile by population within that zone. Sullivan County falls in EPA Radon Region 2, one of 83 counties nationally EPA assigns to that same geologic province.

Zone vs. an actual test

Sullivan County carries a Zone 1 label because its predicted average clears 4 pCi/L outright — three-plus times the 0.4 pCi/L typical outdoors and above the 1.3 pCi/L most homes see. 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 Sullivan County specifically.

If Sullivan County tests above the action level

For a Sullivan 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 New York's state radon program

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

Sullivan 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.