What Is Radon Mitigation? A Homeowner's Complete Guide

What Is Radon?

Radon is a naturally occurring radioactive gas that forms from the decay of uranium in soil and rock. It seeps into homes through foundation cracks, gaps around pipes, floor drains, and construction joints. Because it's colorless and odorless, it's completely undetectable without a test.

The EPA estimates radon causes about 21,000 lung cancer deaths per year in the US — more than drunk driving. It's the second leading cause of lung cancer after smoking, and the leading cause among non-smokers.

What Levels Are Dangerous?

Radon is measured in picocuries per liter (pCi/L). Outdoor air averages around 0.4 pCi/L.

• Below 2 pCi/L: Low risk. Most homes fall here after mitigation.
• 2–4 pCi/L: Elevated. EPA recommends considering mitigation.
• 4 pCi/L and above: EPA action level — mitigate.
• 10+ pCi/L: Significant risk. Prioritize mitigation immediately.
• 20+ pCi/L: High urgency. Can reach dangerous cumulative exposure in months.

Any level above 4 pCi/L warrants a certified mitigator — not a DIY approach.

How Radon Enters Your Home

Radon follows the path of least resistance from soil to air. Common entry points:

• Cracks in foundation slabs and walls
• Floor-wall joints in basements
• Gaps around service pipes and utility penetrations
• Sump pits and floor drains
• Exposed soil in crawl spaces
• Hollow block foundation walls

Homes with basements or crawl spaces tend to have higher radon — these foundation types have more soil exposure and more potential entry points.

What Is Radon Mitigation?

Radon mitigation is the process of reducing indoor radon levels to safe concentrations. The most common method — Sub-Slab Depressurization (SSD) — works by creating negative pressure beneath your foundation, pulling radon out before it can enter your home and venting it harmlessly above the roofline.

A basic SSD system consists of:

• One or more suction points (core holes drilled in the slab or pipes under a crawl space barrier)
• A PVC pipe that routes from the suction point to the exterior
• A continuously running fan that maintains negative pressure
• A warning device (manometer or alarm) that tells you if the fan fails

The fan runs 24/7 on about 20–30 watts — comparable to a night light. Most homeowners never notice it after installation.

The Installation Process

Assessment (1–2 hours): A certified mitigator inspects your foundation, tests sub-slab communication with a vacuum test, and determines the best suction point locations and fan size.

Installation (4–10 hours): Core holes are drilled, pipe is run and connected to the fan, the exterior vent is installed above the roofline, and the warning device is mounted in a visible location.

Verification test (48–96 hours after): A follow-up radon test confirms levels have dropped below 4 pCi/L. Most certified systems achieve below 2 pCi/L.

How Long Does It Last?

The pipe and fittings are essentially permanent. Fans typically last 5–15 years depending on the model and conditions. When a fan fails, the warning device alerts you. Replacement fans cost $100–$250 and take 30 minutes to swap out.

Get your home re-tested every 2 years, or after any major renovation that changes your foundation or ventilation.

DIY vs. Professional

DIY is reasonable for:

• Slab-on-grade foundations
• Radon levels between 4–8 pCi/L
• Homeowners comfortable with basic home improvement (drilling, PVC work)
• States that don't require licensed contractors for mitigation

Always hire a certified pro for:

• Crawl spaces (significantly more complex)
• Radon above 8 pCi/L
• Basement or complex multi-foundation homes
• Finished basements with hidden pipe routing

The average professional job costs $800–$2,500 for a slab or basement, and $2,500–$8,000 for a crawl space. One job lasts the life of the home.

Why Certification Matters

Any contractor can install a pipe and a fan. A certified mitigator knows how to:

• Assess sub-slab communication to place suction points correctly
• Size the fan to the specific conditions (under-powered fans don't work; over-powered ones can cause backdrafting)
• Meet state and AARST installation standards
• Troubleshoot when initial results don't hit target levels

Always verify certification at radonproficiency.org (NRPP) or nrsb.org (NRSB) before signing anything. RadonBase only lists verified, credentialed mitigators.

Find a certified mitigator in your state →