Skip to content
RADON411
$5

County radon report

Get it
Fix5 min read

Can radon be removed completely?

By Radon411 Editorial TeamUpdated How we research

Short answer

Not to zero. Outdoor air holds about 0.4 pCi/L, and the ground under a home keeps producing radon. What a radon system can do is cut indoor levels by up to 99 percent, and most homes can be brought to 2 pCi/L or below. A test after the work shows how much was removed.

Next step: a certified professional designs and installs the fix. Find a mitigation professional

The goal of indoor radon no higher than outdoor air is not yet technologically achievable in every home. Sub-slab suction, the most common method, typically lowers radon by 50 to 99 percent, and even very high levels can be reduced.

Sealing cracks alone, opening windows and ordinary air cleaners do not remove radon reliably. A fan-driven soil suction system does, for as long as it runs.

What to do next: if your test is high, have a qualified contractor install a system, then test again after the work and at least every two years.

Why radon cannot be taken to zero

Radon comes from the natural decay of uranium and radium found in nearly all rocks and soils, so the ground under every home keeps making more. Outdoor air carries some too, about 0.4 . Removing radon from a house means keeping the steady supply from the ground out and diluting what gets in, not deleting it once.

Radon itself does not last: it decays, with a half-life of 3.8 days. But uranium and radium in the soil keep producing it, and radon gas in soils is the principal source of elevated radon in U.S. homes. That steady supply is why a fix has to keep working day after day, and why a radon fan runs all the time.

Radon levels for comparison, in pCi/L
WhereLevel
Outdoor airAbout 0.4 pCi/L
The average indoor levelAbout 1.3 pCi/L
What most homes can be reduced to2 pCi/L or below

Congress set a long-term goal that indoor radon be no higher than outdoor levels. That goal is not yet technologically achievable in all cases, but most homes today can be brought to 2 pCi/L or below.

How much a radon system removes

Some radon reduction systems cut radon levels by up to 99 percent, and even very high levels can be brought down to acceptable levels. The most common and usually most reliable method is sub-slab suction: a fan draws radon from below the home through a pipe and releases it outdoors, while keeping a vacuum under the slab.

Typical radon reduction, EPA

Basement and slab-on-grade homes

  • Subslab suction (subslab depressurization)50 to 99 percentWorks best if air can move easily in material under slab.
  • Passive subslab suction30 to 70 percentMay be more effective in cold climates; not as effective as active subslab suction.
  • Drain tile suction50 to 99 percentCan work with either partial or complete drain tile loops.
  • Block-wall suction50 to 99 percentOnly in homes with hollow block-walls; requires sealing of major openings.
  • Sump-hole suction50 to 99 percentWorks best if air moves easily to sump from under the slab.

Crawlspace homes

  • Submembrane depressurization in a crawlspace50 to 99 percentLess heat loss than natural ventilation in cold winter climates.

Any type of home

  • Natural ventilationVariable/TemporarySignificant heated or cooled air loss; operating costs depend on utility rates and amount of ventilation.
Typical radon reduction by method. Soil suction methods reach the highest reductions; ventilation is variable and temporary.

Because radon keeps coming from the soil, a system only works while it runs: the fan should never be turned off. See does radon mitigation work for what systems achieve, and how to reduce radon for the methods.

What does not remove radon

Approaches that fall short on their own
ApproachWhy it falls short
Sealing cracks aloneNot shown to lower radon significantly or consistently; entry points are hard to find and seal for good, and settling opens new ones
Opening windowsA temporary approach; levels most often return within about 12 hours of closing up
Ordinary air cleanersWithout special media such as activated carbon or alumina, they do not remove gases, including radon
Air cleaners with special mediaWhether they reduce the health risk from radon cannot be adequately assessed at this time

Sealing still has a place: it is part of most radon systems, because it makes them work better. It just is not a fix by itself. Air cleaners are covered in do air purifiers get rid of radon.

Radon in water can be removed too

If radon comes in with well water, it can be taken out of the water before it reaches the taps. Point-of-entry treatment does this, usually with granular activated carbon filters or aeration devices. Radon from the soil is usually the bigger risk, so test the air first.

Typical radon reduction, EPA

Radon in private well water

  • Private well water: aeration95 to 99 percentGenerally more efficient than GAC; requires annual cleaning to maintain effectiveness and to prevent contamination; requires venting radon to outdoors.
  • Private well water: granular activated carbon (GAC)85 to 95 percentLess efficient for higher levels than aeration; use for moderate levels, around 5,000 pCi/L or less in water.
Typical radon removal from water by aeration and by granular activated carbon.

See does radon come from well water and how to get radon out of water.

Proving the radon is gone

Only a test shows how much radon a system removed. Test again after the work is finished, then at least every two years. EPA recommends fixing a home when the radon level is 4 pCi/L or higher. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. Any radon exposure carries some risk, so a lower result is better even below those levels. The first test should be within 30 days of installation, and an independent test, by a separate tester or by you, avoids any conflict of interest.

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.

After a system goes in: a first test within 30 days, then retests at least every two years.

Questions about removing radon

Can radon be removed completely from a house?

Not to zero, since outdoor air holds about 0.4 pCi/L and the ground keeps producing it. Most homes can be brought to 2 pCi/L or below.

How much radon does a mitigation system remove?

Some systems reduce radon by up to 99 percent. Sub-slab suction typically cuts levels by 50 to 99 percent.

Does radon go away on its own?

Radon itself decays, with a half-life of 3.8 days, but uranium and radium in the ground keep producing more, so a high level in a home does not fade without a fix.

Will sealing cracks get rid of radon?

Not on its own. Sealing alone has not been shown to lower radon significantly or consistently, though it helps other methods work. See how to seal cracks in a basement floor.

Can an air purifier remove radon?

Ordinary air cleaners do not remove radon. Whether those with special media such as activated carbon reduce the health risk cannot be adequately assessed at this time.

Can radon come back after mitigation?

Levels can change: normal settling opens new entry routes, and a system works only while its fan runs. Retest at least every two years to be sure levels stay low.

How do I know the radon is gone?

Test after the system is installed, then at least every two years. A low result with the fan running shows the system is working.

Fix

Related guides

How a mitigation system brings a high level down, the fan that runs it, and what it costs.

Everything in FixOther guide topics
  • 23 min read

    Radon remediation system

    What gets rid of radon, how reduction and abatement work, and what they cost.

    Read the guide
  • 23 min read

    Radon fan

    How a radon mitigation fan works, where it goes, what it costs to run and replace.

    Read the guide
  • Overview page

    How radon mitigation works

    How mitigation systems reduce indoor radon, when to mitigate instead of retest, what a project involves, common mistakes, and how to confirm a system actually worked.

    Open the page