King County, TX radon potential

EPA places King County in Zone 3 - Low Potential — a predicted county-wide average indoor radon level below 2 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. That puts King County in the 0th percentile nationally for radon potential — higher than 0% of the counties EPA has rated.

King County by the numbers

King County, Texas is home to about 215 people across 910.873 square miles. Averaged across its land area, King County runs about 0 people per square mile. Within its own EPA zone, King County is bigger by population than 0% of the counties that share it. EPA's geology-based Region 6 groups King County with 502 other counties nationally sharing its underlying rock and soil profile.

Why the zone isn't the answer by itself

King County'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. Don't read Zone 3 as a pass for King County — EPA's guidance to test every home makes no exception for counties predicted low.

If King 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 Texas's state radon program

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

Where King County's figures come from

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.