If you've searched for radon information and landed on a map showing Northern Kentucky shaded as "elevated radon potential," you're not imagining things -- Boone County and Kenton County both carry the EPA's Zone 1 designation. That map is a useful starting point, but it isn't a diagnosis for your specific address. Here's how the zone system actually works and what it means for homes in Florence, Covington, Independence, and the rest of the Madison Pike corridor.
What does it mean that Northern Kentucky is in an EPA "elevated radon potential" zone?
It means the U.S. Environmental Protection Agency's Map of Radon Zones classifies the county as Zone 1, predicting an average indoor screening level above 4 picocuries per liter (pCi/L) -- the EPA's radon action level. This zone rating is a planning tool based on geology and aerial radiometric data, not a substitute for testing your specific home.
The map was built in the early 1990s using a combination of indoor radon measurements collected at the time, soil permeability data, and airborne radiometric surveys that measure natural gamma radiation from the ground. Counties were then sorted into three tiers: Zone 1 (predicted average above 4 pCi/L), Zone 2 (2 to 4 pCi/L), and Zone 3 (below 2 pCi/L). It's a county-level statistical prediction, produced once, not an ongoing monitoring network.
Which Northern Kentucky counties fall inside the EPA Zone 1 radon designation?
Boone County and Kenton County, along with most of the rest of Kentucky, carry the EPA's Zone 1 rating for elevated radon potential, based on the agency's county-level Map of Radon Zones. Zone 1 status applies to the whole county, so homes in Florence, Covington, Independence, and the surrounding Madison Pike corridor all fall under the same predicted-elevated designation.
That's consistent with what's documented elsewhere in this region's geology -- Kentucky as a whole has one of the higher concentrations of Zone 1 counties of any state, largely tied to karst limestone bedrock. If you want the county-by-county breakdown for the rest of the state, see our guide on which Kentucky counties have the highest radon, and for the geological "why" behind it, our piece on Inner Bluegrass karst geology covers the mechanism.
Does an EPA Zone 1 rating mean my house definitely has high radon?
No. Zone 1 is a county-wide statistical prediction, not a room-by-room measurement -- some homes in Zone 1 counties test low, and some homes in lower-zone counties test high because radon levels depend on a house's foundation type, soil contact, and ventilation. The only way to know your actual level is a test placed inside the home.
Radon enters through cracks in the slab, sump pits, gaps around utility penetrations, and even through well water in some rural systems. A two-story home with a finished basement over solid rock can test completely differently than the house next door with a crawlspace. Zone maps tell you the odds are worse in your area; they can't tell you your number.
How do I get a certified radon test if I live in Florence, Covington, or elsewhere in Boone or Kenton County?
Look for a tester holding current National Radon Proficiency Program (NRPP) or National Radon Safety Board (NRSB) certification, and place a continuous monitor or charcoal canister on the lowest livable level of the home for at least 48 hours, following EPA testing protocol, with doors and windows closed except for normal entry and exit.
Short-term test devices should sit at least 20 inches off the floor, away from exterior walls, drafts from HVAC vents, and direct sunlight, per the EPA's testing guidance for homeowners. If you're buying or selling in Boone or Kenton County, our detailed walkthrough on verifying a certified radon tester near you covers exactly what credentials and documentation to ask for before a real estate closing, including how disclosure obligations under KRS 324.360 come into play.
What happens if my Kentucky home tests above 4 pCi/L?
A confirmed reading at or above 4 pCi/L -- the EPA action level -- typically calls for a mitigation system, most often sub-slab depressurization: a sealed vent pipe and inline fan that pull soil gas from beneath the foundation and exhaust it above the roofline, consistent with ASTM E2121 mitigation system standards. Retesting after installation confirms the system brought levels down.
Sub-slab depressurization is the most common approach for homes with a poured basement or slab-on-grade foundation, which describes a large share of the housing stock across Florence, Covington, and Independence. Crawlspace homes typically need a variation with a heavy vapor barrier sealed to the foundation walls before the vent system is added. A licensed operator in your area can walk the foundation and tell you which configuration applies -- system design isn't one-size-fits-all even within the same Zone 1 county.
This article is general educational information about EPA radon zone classifications and testing/mitigation practices in Kentucky, not a substitute for an actual test result, a licensed inspection, or legal advice on real estate disclosure obligations. Radon test placement, mitigation design, and system installation should be handled by an independent licensed operator qualified for your specific property.