How radon mitigation works

Radon mitigation means reducing the radon that gets into a building, usually by drawing soil gas from beneath the foundation and venting it outside before it enters your living space. EPA recommends fixing a home that tests at 4 pCi/L or higher. The work is well established, and the Tennessee Radon Program strongly recommends hiring a certified professional to do it.

When should I fix my home?

Fix your home if the average of two short-term tests, or any long-term test, is 4 pCi/L or higher (CDC). If your level is between 2 and 4 pCi/L, EPA recommends considering a fix. Not sure? Use the result interpreter.

How does a radon reduction system work?

Most systems work by changing the air pressure under the house so radon is pulled away from the living space instead of into it.

• Sub-slab depressurization (homes with a basement or slab floor): a pipe is set into the gravel or soil beneath the floor, and a fan draws soil gas through the pipe and releases it above the roof.
• Sub-membrane depressurization (homes with a crawlspace): plastic sheeting covers the crawlspace soil, and a pipe and fan draw gas from beneath the sheeting.
• Sump-based systems: an existing sump pit can be sealed and used as the suction point.
• Sealing: cracks and openings in the foundation are sealed to help the system work.

These descriptions follow the definitions in the International Residential Code's radon-control appendix (IRC Appendix AF) and the methods listed by the World Health Organization and the American Lung Association. WHO notes that passive systems, which rely on natural airflow, can cut indoor radon by more than half, and adding a fan reduces levels further.

Professionals follow the national standard for existing homes, ANSI/AARST SGM-SF-2023, Soil Gas Mitigation Standards for Existing Homes (AARST standards).

How much does radon mitigation cost?

The American Lung Association cites a typical range of roughly $1,000 to $2,500 or more (ALA). This is a national estimate; your price will depend on your foundation type, how easily gas moves under your floor, and where the pipe can run. Get more than one quote. See our mitigation cost page.

How do I find a qualified radon mitigation professional?

Tennessee doesn't require state licensing or certification for radon mitigators (Indoor Environments Association, 2024). That makes checking credentials your job. The Tennessee Radon Program points residents to two national directories (TDEC):

• NRPP professional search
• NRSB professional directory

NRPP-certified professionals must work to ANSI/AARST standards and renew their certification every two years (NRPP). Both organizations take consumer complaints.

What should I ask before hiring someone?

• Are you certified for radon mitigation by NRPP or NRSB? Can I see your certification number?
• Will the system be installed to ANSI/AARST SGM-SF-2023?
• What type of system do you recommend for my foundation, and why?
• Where will the pipe and fan go, inside and outside the house?
• Is a follow-up radon test included after installation?
• How will I know the system is working, and what maintenance does it need?
• What does the warranty cover, and for how long?

More detail: how to evaluate a mitigation quote.

How do I know the system worked?

Test again after the system is installed. CDC advises retesting a few months after a fix (CDC), and the American Lung Association recommends retesting every two years after that. You can use the free state kit for these follow-up tests. See after mitigation.

Frequently asked questions

Can I install a system myself? It's legal in Tennessee, but the state program strongly recommends a certified professional. A poorly designed system may not lower radon enough.

Will a radon system lower my level to zero? No. Outdoor air itself averages about 0.4 pCi/L, and EPA notes that reducing indoor levels below 2 pCi/L is difficult (EPA). The goal is the lowest level reasonably possible.

Does opening windows fix radon? Better ventilation is one way to reduce radon, according to WHO, but open windows only help while they stay open. For a lasting fix, use a system designed for your home.

Next step: Find a certified radon professional →

Sources: EPA – Health Risk of Radon · CDC – Testing for Radon · American Lung Association – Radon · WHO – Radon fact sheet · ANSI/AARST Standards · IRC Appendix AF (as published by Seattle) · Tennessee Radon Program · NRPP · NRSB · Indoor Environments Association, 2024

Last reviewed October 17, 2026 by the Tennessee Radon Authority editorial team. How we research.