Is Harrison County, MS a radon risk area?

EPA places Harrison 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 Harrison County in the 29th percentile nationally for radon potential — higher than 29% of the counties EPA has rated.

How Harrison County compares

About 213,730 people live in Harrison County, Mississippi, spread over 573.65 square miles. Population density there runs about 373 people per square mile. Rank 119 by population within its EPA zone puts Harrison County at the 89th percentile among zone peers. Harrison County falls in EPA Radon Region 4, one of 736 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, Harrison County's Zone 3 prediction is the low end of the scale. A Zone 3 rating means Harrison County's county-wide average is predicted low, but EPA is explicit that a meaningful share of homes in low-potential zones still test above the action level — a low zone is not a reason to skip testing.

Testing and mitigation in Harrison County

Nothing about Harrison 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 Mississippi's state radon program

Harrison County's test kit answers today; a Airthings radon monitor keeps answering for Harrison 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

The methodology guide shows exactly which EPA and Census sources feed Harrison County's numbers. Whatever zone Harrison County carries, the zone explainer covers what it does and doesn't tell you about any one house.