Waukesha County, WI radon potential

EPA places Waukesha 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. Rank it against the rest of the country and Waukesha County lands in the 98th percentile for radon potential.

How Waukesha County compares

Waukesha County, Wisconsin is home to about 417,029 people across 549.727 square miles. That works out to roughly 759 people per square mile. Within its own EPA zone, Waukesha County is bigger by population than 95% of the counties that share it. Waukesha County falls in EPA Radon Region 5, one of 524 counties nationally EPA assigns to that same geologic province.

Why the zone isn't the answer by itself

Waukesha 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. Being in Zone 1 raises the odds Waukesha County homes test above the action level, but it does not mean any specific house does — EPA recommends every home be tested, in every zone, because the only way to know is to test.

If Waukesha 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 Wisconsin's state radon program

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

Where Waukesha 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.