The EPA radon zone map classifies US counties into three risk zones based on predicted average indoor radon levels. Radon is a naturally occurring radioactive gas that can accumulate in homes — it's the second leading cause of lung cancer in the US after smoking. Knowing your zone tells you how urgently to test.
Health note: The EPA recommends testing ALL homes for radon, regardless of zone. Testing takes 2-7 days with a $15-25 kit from any hardware store.
Look Up Your State's Radon Risk
EPA Radon Zone Definitions
Radon Testing and Mitigation Guide
The EPA radon zone lookup provides state-level risk guidance. Radon is a colorless, odorless radioactive gas produced by uranium decay in soil and rock. It enters homes through cracks in foundations, drains, and gaps around pipes. Long-term exposure is the second leading cause of lung cancer — about 21,000 deaths per year in the US.
How to Test for Radon
Short-term kits (charcoal canisters, 2-7 days) are available at hardware stores for $15-25. Place in the lowest livable area, keep windows closed during the test, then mail to a laboratory. Results return in 1-2 weeks. If the result is 4 pCi/L or higher, do a long-term test (90+ days) to confirm before investing in mitigation.
Radon Mitigation Options
Sub-slab depressurization (ASD) is the standard mitigation method — a contractor installs a pipe through the concrete slab and a continuously running fan to exhaust radon below the house to the outside. This typically reduces radon by 50-99% and costs $800-2,500. Sealing cracks alone is insufficient. The EPA recommends hiring a state-certified radon mitigation contractor.
Frequently Asked Questions
Is this radon zone lookup free?
Yes, completely free with no signup required. Find your EPA radon risk zone by state instantly.
What is a safe radon level in a home?
The EPA action level is 4 pCi/L (picocuries per liter) — at this level, mitigation is recommended. The EPA also suggests considering mitigation at 2-4 pCi/L. The average US indoor radon level is about 1.3 pCi/L; outdoor air is about 0.4 pCi/L. There is no completely safe level, but below 2 pCi/L is generally considered acceptable.
What is EPA Radon Zone 1?
EPA Radon Zone 1 counties have a predicted average indoor radon screening level greater than 4 pCi/L (the action level). Zone 1 represents the highest risk and includes large parts of the Midwest, Mountain West, Pennsylvania, and New York.
How do I test my home for radon?
Short-term radon tests (2-7 days using charcoal canisters) are the easiest starting point. They're available at hardware stores for $15-25. Long-term tests (90+ days using alpha track detectors) give more accurate annual average levels. Test in the lowest livable area of your home — basement or first floor.
How much does radon mitigation cost?
Sub-slab depressurization (the most common mitigation method) typically costs $800-2,500 depending on home size and foundation type. It involves installing a pipe through the foundation slab and a fan to exhaust radon from under the home to the outside. This method reduces radon by 50-99%.
Does every Zone 1 state home have high radon?
No. EPA zones indicate average predicted risk at the county level — individual homes vary significantly. A Zone 1 county means testing is strongly recommended, but your specific home could test low or high. Even Zone 3 homes should test at least once, especially before buying or selling.