Radon Potential (v1)
Version 1.0.0 · Published 2026-06-19
What this is
Radon is a naturally occurring radioactive gas and the second-leading cause of lung cancer. This category reports the radon potential of the property's county from the EPA Map of Radon Zones. We frame it deliberately gently: unlike flood or a contaminated site, radon is cheap to test (a $15 kit) and cheap to fix (a sub-slab depressurization system runs roughly $1,000 to $2,000), so it informs the grade rather than tanking it.
Data source
The EPA Map of Radon Zones assigns every US county a zone from its predicted average indoor radon level. The map is county-granularity because no free property-level radon dataset exists; an actual measurement requires a test in the home. We resolve which county a property falls in and read its EPA zone.
Zones and tiers
| EPA zone | Predicted average | Our tier |
|---|---|---|
| Zone 1 (high) | > 4 pCi/L | moderate, test and mitigate |
| Zone 2 (moderate) | 2 to 4 pCi/L | minor, worth a test |
| Zone 3 (low) | < 2 pCi/L | none, a test is still recommended |
Florida specifics
Per the EPA map, no Florida county is Zone 1. Nine counties are Zone 2 (moderate potential): Alachua, Citrus, Columbia, Hillsborough, Leon, Marion, Miami-Dade, Polk, and Union. The other 58 counties are Zone 3 (low). A Zone 2 county surfaces as a minor, informational flag, it does not by itself lower the grade.
Source: EPA Map of Radon Zones. The EPA stresses that homes with elevated radon have been found in all three zones, so every home should be tested regardless of its county zone.