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Owning and renting4 min read

How often should I test for radon?

By Radon411 Editorial TeamUpdated How we research

Short answer

Test every home at least once, then again when something changes: after a radon fix and at least every two years after that, after major renovations, and when you start living on a lower level. After a low result, you may want to test again sometime in the future.

Next step: check the rules where you rent or let. Radon rules for rentals by state

How often should you get your house tested for radon? There is no fixed yearly schedule for a home without a radon system. Retest on a lower floor if you start living there, before and after a renovation, and when you buy or sell, since a buyer may ask for a new test if the last one is more than about two years old.

A home with a system has a schedule: test within 30 days of installation to confirm it works, then at least every two years. Radon levels vary from day to day and season to season, and houses change, so one old result cannot stand in for a current one.

What to do next: if the home has never been tested, start with a in the lowest lived-in level, and keep your results with your home records.

When to test, at a glance

There is no fixed yearly schedule for a home without a radon system. Test once to find out where you stand, then test again when something changes: the house, the way you use it, or its owner. A home with a system has a schedule of its own.

When to test or retest
SituationWhen to test
Never tested, or the level is unknownNow
After a radon fixWithin 30 days of installation, then at least every two years
Before and after renovatingBefore the work starts and again after it is finished
You start using a lower floorRetest on that level, for example after turning a basement into a bedroom or office
After heating, ventilation or air-conditioning changesRetest; such changes might affect radon levels
Buying or sellingTest during the sale; a buyer may ask for a new test if the last one is more than about two years old
A new homeAs soon as possible after you move in, even if it was built radon-resistant
Your result was lowYou may want to test again sometime in the future

Why one test is not forever

Radon levels vary from day to day and season to season, and even from hour to hour within one building. A single is a snapshot. Houses change too: settling opens new cracks, renovations can change the level of radon in any home, and moving into the basement puts people closer to the ground, where levels are usually higher.

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 after a first short-term result: a high result gets a follow-up test before any decision.

So the first test answers today's question, and a high short-term result is followed by a second test before a decision. A , which runs more than 90 days, gives a better picture of the year-round level. See how long a radon test takes.

If your home has a mitigation system

A radon system changes the schedule. Test once after installation to confirm it worked, ideally by an independent tester, and then at least every two years to make sure the level stays low. In between, the system's warning device, usually a manometer, tells you whether the fan is working; if it shows a problem, call a contractor.

Timeline after a radon mitigation system is installed: the fan runs continuously, test no sooner than 24 hours and within 30 days, then retest at least every two years.
Read this figure as text

  1. Day of installation

    The system goes in

    Keep the fan running at all times: it must run continuously for the system to work correctly.

  2. No sooner than 24 hours

    Earliest post-mitigation test

    Test no sooner than 24 hours after your system is in operation with the fan on, if it has one.

  3. Within 30 days

    Post-mitigation test done

    A two- to seven-day measurement is recommended, and EPA recommends an independent follow-up radon measurement as well as any test the contractor runs.

  4. At least every two years

    Retest

    Retest your home at least every two years to be sure radon levels remain low.

Test conditions: Windows and doors must be closed 12 hours before and during the test, except for normal entry and exit. Not drawn to scale.

After a remodel. After you remodel, retest in the lowest lived-in area to make sure the construction did not reduce the effectiveness of the radon reduction system.

Testing after a mitigation system is installed: the first check, then retests at least every two years and after any remodel.

A remodel also calls for a retest: after major changes, test the lowest lived-in area to make sure the work did not reduce the system's effectiveness. More on the first check is in how long after radon mitigation can you retest.

Testing around a home sale

A sale is its own trigger. Sellers do best to test early and keep the results; buyers often want a recent test, by someone not involved in the sale, in the lowest level they might use.

When a buyer may ask for a new test
ReasonWhy it matters
The last test is not recent, for example more than two years oldLevels and the house may have changed since
The home was renovated or altered after the testRenovations can change radon levels
The buyer will live on a lower level than was testedLower levels, near the ground, often have more radon
The testing checklist was not followedAn improperly run test may be inaccurate

The full picture for buyers and sellers is in the buying a house with radon guide.

Questions about how often to test

Should I test for radon every year?

Not necessarily. Without a radon system there is no set yearly schedule: test again when the house or the way you use it changes. With a system, retest at least every two years.

My test was low. Do I need to test again?

Not on a schedule, but you may want to test again sometime in the future, and you should retest if you start living on a lower level or renovate.

How often should a house with a mitigation system be tested?

At least every two years after the first post-installation test, and again after any remodel.

Do I need to retest after replacing my furnace or air conditioning?

It is a good idea: changes to heating, ventilation and air conditioning might affect radon levels, and a buyer may ask what changed since the last test.

Does a new home need a radon test?

Yes. Every new home should be tested as soon as possible after occupancy, even one built with radon-resistant features.

Should I test in a different season?

Levels vary by season, so a single short-term test cannot show the whole year. A long-term test, more than 90 days, is the better measure of the year-round average.

Owning and renting

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