Radon mitigation · how the system works
How a radon mitigation system works
Most systems are the same idea: make the air under the floor lower in pressure than the house, so soil gas goes up a pipe instead of into the rooms. The parts, the gauge, and the rules installers work to, from EPA and the state programs.
The parts and the methods
- Vent pipe and fan system
- The main fix is a vent pipe and fan that pull radon from beneath the house and send it outside.U.S. Environmental Protection Agency, read October 15, 2026
- Subslab depressurization
- Active subslab suction, also called subslab depressurization, is the most common and usually most reliable method.U.S. Environmental Protection Agency, read October 15, 2026
- Crawl space: submembrane
- For crawl spaces, a plastic sheet over the earth floor with a vent pipe and fan beneath it is the most effective method.U.S. Environmental Protection Agency, read October 15, 2026
- Sealing alone not enough
- Sealing cracks helps other methods, but EPA does not recommend sealing by itself.U.S. Environmental Protection Agency, read October 15, 2026
The gauge and the fan
Many systems use a U-tube gauge (a manometer) on the pipe as that warning device. Ask the installer what yours reads while the fan runs, so you can tell when it changes.
- Warning device required
- An active system must have a warning device that shows if it stops working properly.U.S. Environmental Protection Agency, read October 15, 2026
- Fan lifespan
- Radon fans may last five years or more and may then need repair or replacement.U.S. Environmental Protection Agency, read October 15, 2026
After the system goes in
- Post-mitigation test window
- After a system goes in, test within 30 days but not sooner than 24 hours after it starts running.U.S. Environmental Protection Agency, read October 15, 2026
- Independent post-fix tester
- EPA recommends the after-mitigation test be done by an independent, qualified radon tester.U.S. Environmental Protection Agency, read October 15, 2026
- Retest every two years
- With a system in place, EPA suggests retesting at least every two years.U.S. Environmental Protection Agency, read October 15, 2026
Rules installers work to
- State mitigation standards
- Pennsylvania has its own Radon Mitigation Standards that set uniform rules for designing, installing and checking home radon systems.Pennsylvania Department of Environmental Protection, read October 15, 2026
- Tests before and after
- A mitigator must test the building before and after the work, and each test must run at least 48 hours.PA Environmental Quality Board, 2018 final rule text (posted by DEP), read October 15, 2026
- System label
- A system description label must be fixed to the radon system piping, readable from at least 3 feet away.PA Environmental Quality Board, 2018 final rule text (posted by DEP), read October 15, 2026
- Fan location
- A radon fan may not go below grade, in a window well, or inside the heated or cooled living space.PA Environmental Quality Board, 2018 final rule text (posted by DEP), read October 15, 2026
- Mitigation standard
- A licensed mitigation professional must install, modify and repair systems to the applicable ANSI/AARST radon mitigation standard.Colorado General Assembly (Session Laws 2021, ch. 398, HB21-1195), read October 15, 2026
- Mitigators cannot test own work
- A mitigator who also holds a measurement license may not do the before or after tests at a house where they installed the system, unless another independent person has measured.Illinois General Assembly, Joint Committee on Administrative Rules (Illinois Administrative Code), read October 15, 2026
- Who may install and activate
- The builder or its subcontractors may install the passive pipe, but only a licensed radon contractor may add a vent fan or turn it into an active system.Illinois General Assembly (Illinois Compiled Statutes), read October 15, 2026
- Use a qualified mitigator
- EPA recommends a certified or qualified radon mitigation contractor trained to fix radon problems.U.S. Environmental Protection Agency, read October 15, 2026
What licensed mitigators charge · Check a mitigator's license · Passive systems in new homes
Sources
- U.S. Environmental Protection Agency, read October 15, 2026.
- U.S. Environmental Protection Agency, read October 15, 2026.
- U.S. Environmental Protection Agency, read October 15, 2026.
- Pennsylvania Department of Environmental Protection, read October 15, 2026.
- PA Environmental Quality Board, 2018 final rule text (posted by DEP), read October 15, 2026.
- Colorado General Assembly (Session Laws 2021, ch. 398, HB21-1195), read October 15, 2026.
- Illinois General Assembly, Joint Committee on Administrative Rules (Illinois Administrative Code), read October 15, 2026.
- Illinois General Assembly (Illinois Compiled Statutes), read October 15, 2026.