Franklin County, WA radon potential

EPA's own radon map rates Franklin County zone 2 - moderate potential, predicting a county-wide average indoor level between 2 and 4 pCi/L. Nationally, Franklin County ranks higher in radon potential than 60% of rated counties (the 60th percentile).

How Franklin County compares

Franklin County, Washington is home to about 101,238 people across 1,241.596 square miles. Population density there runs about 82 people per square mile. Within its own EPA zone, Franklin County is bigger by population than 81% of the counties that share it. Franklin County falls in EPA Radon Region 10, one of 142 counties nationally EPA assigns to that same geologic province.

Why the zone isn't the answer by itself

Call it a middle case: above the 1.3 pCi/L most US homes average, below the 4 pCi/L line EPA uses to recommend mitigation — that's Franklin County's Zone 2 prediction. Franklin County's Zone 2 rating sits in the middle nationally; EPA's guidance is unchanged by that — test every home regardless of its zone.

If Franklin 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 Washington's state radon program

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

Where Franklin County's figures come from

Franklin County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.