Sullivan County, PA radon potential

EPA's own radon map rates Sullivan County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. Nationally that's the 72nd percentile for radon potential — Sullivan County outranks 72% of every county EPA has rated.

Sullivan County by the numbers

Sullivan County, Pennsylvania is home to about 5,927 people across 449.939 square miles. That works out to roughly 13 people per square mile. Within its own EPA zone, Sullivan County is bigger by population than 17% of the counties that share it. EPA's geology-based Region 3 groups Sullivan County with 244 other counties nationally sharing its underlying rock and soil profile.

Zone vs. an actual test

Sullivan 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. A Zone 1 rating means testing is worth doing sooner rather than later, but it is still county-wide average, not a reading for any single house — some homes in Sullivan County will test well under the action level, and EPA's guidance is to test regardless of zone.

If Sullivan County tests above the action level

A short-term test kit is the standard first step and typically costs far less than mitigation itself. If a test comes back at or above 4 pCi/L, a radon mitigation system for a typical home runs roughly $800–$2,500 (around $1,200 for a common single-family install), driven mainly by foundation type, not by county.

Find Pennsylvania'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. RADONZONE-10OFF at checkout knocks 10% off.

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.