Is Hawaii County, HI a radon risk area?

EPA's own radon map rates Hawaii County zone 3 - low potential, predicting a county-wide average indoor level below 2 pCi/L. Nationally, Hawaii County ranks higher in radon potential than 29% of rated counties (the 29th percentile).

Hawaii County by the numbers

About 209,790 people live in Hawaii County, Hawaii, spread over 4,028.431 square miles. That works out to roughly 52 people per square mile. Rank 125 by population within its EPA zone puts Hawaii County at the 88th percentile among zone peers. Hawaii County falls in EPA Radon Region 9, one of 95 counties nationally EPA assigns to that same geologic province.

Zone vs. an actual test

Well clear of both the 1.3 pCi/L national indoor average and EPA's 4 pCi/L action level, Hawaii County's Zone 3 prediction is the low end of the scale. Don't read Zone 3 as a pass for Hawaii County — EPA's guidance to test every home makes no exception for counties predicted low.

Next steps for a home in Hawaii County

Nothing about Hawaii County's EPA zone changes the mitigation number: $800–$2,500 nationally (around $1,200 typical), set by the house's foundation rather than the county it sits in — and only relevant once a test actually clears 4 pCi/L.

Find Hawaii's state radon program

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

More on how this number was built

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. Whatever zone Hawaii County carries, the zone explainer covers what it does and doesn't tell you about any one house.