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Buying and selling5 min read

Should I buy a home with a radon mitigation system already installed?

By Radon411 Editorial TeamUpdated How we research

Short answer

Yes, it can be a good sign: a system means a radon problem was found and fixed, and where radon problems have been fixed, home sales have not been blocked. Before you buy, ask the seller for the system's paperwork and test results, check the warning device, and test with the fan running.

Next step: see how a radon test fits a home sale. Testing for a home sale

A system only protects the home while it works. Look for a clear label, a warning device such as a manometer, a fan outside the living space and an exhaust above the roof, and ask whether any warranty transfers to you.

Then test. Make sure the vent fan is operating properly, have it repaired first if it is not, and keep the system running for the whole test, placed in the lowest level you might use regularly.

What to do next: request the seller's results and system information now, and book a test with the system on as part of your inspection period.

What an installed system tells you

A radon system in a house for sale means someone found a radon problem and dealt with it. That is not a reason to walk away: where radon problems have been fixed, home sales have not been blocked, and the added protection can be a selling point. What matters is whether the system is working now, and what today's level is.

Cross-section of a house with a sub-slab depressurization system: soil gas drawn from beneath the slab into a suction point, up a vent pipe, through a fan outside the living space and out above the roofline.
Read this figure as text
Sub-slab depressurization system in a house cross-sectionGround levelLiving spaceBasement12345
  1. Soil gas drawn from beneath the slab
  2. Suction point through the slab
  3. Vent pipe
  4. Fan, outside the living space
  5. Discharge above the roofline
A typical active system: a suction pipe through the floor, a fan outside the living space, an exhaust above the roof and a warning device.

Most systems are active soil depressurization: a continuously running fan draws radon from under the building through a pipe and vents it above the roof, keeping it out of the home. If the house has only passive radon-resistant piping, a vent fan can easily be added to make it active if a test comes back high.

What to ask the seller

Know the indoor radon level of any home you consider buying. Ask the seller for their test results and for any information they have about the system; a seller is expected to pass on details of the system's operation and maintenance.

Questions for the seller
Ask forWhy
Test results before and after the system went inTo see what the system achieved, and who did the testing: the homeowner, a professional or someone else
The date of the last testA buyer may want a new test if the last one is more than about two years old
Written operating and maintenance instructionsSo you know how the system works and what it needs
Warranties, and whether they transfer to a new ownerFan warranties tend not to exceed five years, and the contract should say whether they transfer
Changes since the testRenovations or heating and cooling changes might affect radon levels
The installer's detailsFor service, and for questions the paperwork does not answer

What to check in the house

A walk-through checklist for an installed system
CheckWhat to look for
LabelsThe system should be clearly labeled, so no one changes it by accident
Warning deviceThere should be one, usually a manometer, where it can be seen or heard; even fluid levels in a u-tube manometer mean the fan stopped or something else is not working
Fan locationNot in or below a livable area; usually in an attic, garage or outside
ExhaustVenting above the surface of the roof and 10 feet or more above the ground
Fan runningIt should run all the time; a system only works with the fan on
The paperwork on the systemMinnesota, for one, requires an operating and maintenance document attached to the system for current and future occupants

Test with the system running

A current test is the way to know today's level. Before testing, make sure the vent fan is operating properly; if it is not, have it repaired and then test. The system should be working and running for the whole test, and the test should go in the lowest level you might use regularly.

Flowchart of EPA's radon testing steps: take a short-term test; at or above 4 pCi/L follow up with a long-term or a second short-term test; then fix the home or consider fixing based on the result or the average of the two tests.
Read this figure as text

  1. 1Step 1: Take a short-term test.

    • Below 4 pCi/LEven if your test result is below 4 pCi/L, you may want to test again sometime in the future.
    • At or above 4 pCi/LIf your result is at or above 4 pCi/L, take a followup test to be sure.

  2. 2Step 2: Follow up with either a long-term test or a second short-term test.

    • Long-term testFor a better understanding of your year-round average radon level, take a long-term test.
    • Second short-term testIf you need results quickly, take a second short-term test. If your first short-term test result is more than twice EPA's 4 pCi/L action level, you should take a second short-term test immediately.

  3. 3Step 3: Decide whether to fix your home.

    • After a long-term testFix your home if your long-term test result is 4 pCi/L or more.
    • After a second short-term testConsider fixing your home if the average of your first and second test is at or above 4 pCi/L.
The testing steps if a result comes back high, even with a system in place.

EPA recommends fixing a home when the radon level is 4 or higher. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. A high result with a system in place means the system needs attention or more work, not that it cannot be fixed. Independent testing avoids any conflict of interest. Test options for a sale are in should I get a radon test with my home inspection.

Living with the system after you buy

Owning a radon system
TaskHow often
Check the warning device or monitorsRegularly; Minnesota asks owners to check both monitors monthly
Retest the homeAt least every two years, and after any remodel
Replace the fanFans may last five years or more and then need repair or replacement
Plan renovationsAsk the radon contractor whether major changes could void any warranties

Like a furnace or chimney, a radon system needs occasional maintenance, and running the fan slightly raises the electric bill. If the warning device shows a problem, check that the monitor tubing is connected and not kinked and that the fan has power, then call a contractor. Whether you can ever switch it off is answered in can I turn off my radon system.

Questions about buying a home with a radon system

Is a radon mitigation system a red flag?

No. It means a problem was found and addressed. Where radon problems have been fixed, home sales have not been blocked, and the added protection can be a selling point.

Should I still test a house that has a radon system?

Yes. Make sure the fan is working, then test with the system running for the whole test. The result tells you whether the system is doing its job.

How do I know if the radon system is working?

Look at the warning device: on a u-tube manometer, even fluid levels mean the fan stopped or something else is wrong. The gauge shows suction, not radon, so test as well. See how to read a radon test.

Does the warranty transfer to me?

It depends on the contract; a good one states whether warranties or guarantees transfer when the home is sold. Ask the seller for the paperwork.

How long does a radon fan last?

Fans may last five years or more, and manufacturer warranties tend not to exceed five years. See the radon fan guide.

What if the test is high even with the system?

Call a qualified mitigation contractor to check it; more work may be needed to bring the level down. Even very high levels can be reduced.

Buying and selling

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Radon in a home sale: testing before closing, the inspection, disclosure and negotiation.

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