Is My Home at Risk for Radon?

What is radon and why does it matter?

Radon is a radioactive gas that forms naturally from the decay of uranium in soil and rock. It seeps into homes through foundation cracks, sump pits, and utility penetrations. Because it's colorless and odorless, you can't detect it without testing.

The EPA estimates that radon causes approximately 21,000 lung cancer deaths per year in the United States — making it the second leading cause of lung cancer after smoking. One in fifteen homes in the US has elevated radon levels.

What is the EPA action level for radon?

The EPA recommends taking action to reduce radon if your home tests at 4 pCi/L or higher (picocuries per liter). They also suggest considering mitigation at levels between 2–4 pCi/L. The average indoor radon level in US homes is 1.3 pCi/L; the average outdoor level is 0.4 pCi/L.

What are EPA radon zones?

The EPA divides US counties into three zones based on predicted average indoor radon levels:

• Zone 1 — Highest potential. Predicted average above 4 pCi/L. States with significant Zone 1 coverage include Iowa, Illinois, Ohio, Pennsylvania, Colorado, Montana, Wyoming, and Michigan.
• Zone 2 — Moderate potential. Predicted average between 2–4 pCi/L.
• Zone 3 — Lower potential. Predicted average below 2 pCi/L. Includes much of Florida, Hawaii, and the Gulf Coast.

Zone designation is based on geology, soil type, building characteristics, and local measurements. Even in Zone 3, individual homes can have high radon — testing is the only way to know for sure.

How does foundation type affect radon risk?

Homes with basements are at higher risk because the living space is closer to the soil where radon originates. Radon enters through:

• Cracks in concrete floors and walls
• Gaps around service pipes and utility penetrations
• Sump pits and floor drains
• Hollow block foundation walls

Crawl space homes can also have elevated radon, particularly if the crawl space is unventilated. Slab-on-grade homes generally have lower risk, but can still have elevated levels depending on soil conditions and construction quality.

How is radon fixed?

The most common and effective solution is a sub-slab depressurization system (also called active soil depressurization). A certified mitigator installs a pipe through the foundation floor connected to a fan that draws radon from beneath the home and vents it outside before it can enter. This system:

• Typically reduces radon by 90% or more
• Costs $800–2,500 installed
• Runs quietly 24/7 with electricity costs of $20–30/year
• Works in virtually any home regardless of construction type

How do I find a certified radon mitigator?

Radon mitigation requires certification in most states. Look for contractors certified by the NRPP (National Radon Proficiency Program) or NRSB (National Radon Safety Board) — the two nationally recognized radon certification bodies.

RadonBase lists 3,052 NRPP and NRSB certified mitigators across all 50 states, verified against official certification databases. Search by state to find certified professionals near you.