What EPA's radon map says about Kauai County

Kauai County is mapped as Zone 3 - Low Potential by EPA — meaning the county-wide average indoor level is predicted below 2 pCi/L. Rank it against the rest of the country and Kauai County lands in the 25th percentile for radon potential.

Kauai County by the numbers

About 73,840 people live in Kauai County, Hawaii, spread over 619.84 square miles. Averaged across its land area, Kauai County runs about 119 people per square mile. Among counties sharing Kauai County's EPA zone, it outranks 75% of them by population. EPA's geology-based Region 9 groups Kauai County with 94 other counties nationally sharing its underlying rock and soil profile.

Zone vs. an actual test

Kauai 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. Even at Zone 3, Kauai County homes are not guaranteed a low reading — zone is a county-wide average, and EPA recommends testing every home regardless of zone.

Next steps for a home in Kauai County

Mitigation cost doesn't depend on Kauai County's zone — it depends on the house's foundation. A typical system runs $800–$2,500 (about $1,200 typical), and testing first is what tells you whether that's needed at all.

Find Hawaii's state radon program

Kauai County's test kit answers today; a Airthings radon monitor keeps answering for Kauai County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. RADONZONE-10OFF at checkout knocks 10% off.

More on how this number was built

Kauai 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.