HomeMaintList

How often should you test your home for radon?

Updated

Short answer

Test for radon every 2 years. Test again after a renovation, a new addition or a finished basement, since any of those changes how air moves through the house. The test is a small kit left in the lowest lived-in level for a few days and mailed to a lab, and winter, with the windows shut, is the time to do it. Setting it up takes 10 to 15 minutes, a kit costs $15 to $50, and a professional test runs $150 to $300.

Why it matters

Radon is a radioactive gas that comes out of the ground everywhere, in amounts that vary from one house to the next on the same street. It seeps up through cracks in the slab, gaps around pipes, and sump pits, and it collects in the lowest level of the house. It has no smell, no color and no taste, and the only effect of breathing it is on the lungs, years later. It's the second leading cause of lung cancer after smoking, and the leading cause among people who've never smoked.

The level in a house changes. The soil shifts, the house settles and opens new cracks, a finished basement puts people where the gas is, and a new furnace or a sealed-up renovation changes the pressure that draws it in. A house that tested fine years ago may not now. The test is cheap, the fix, a mitigation system that vents the gas from under the slab, is well understood, and the gap between them is the reason to test every 2 years rather than once.

When to do it more often

The index gives one modifier: test again after a renovation, a new addition or a finished basement. Each changes the house's airflow or puts people in the lowest level, where the gas collects. Beyond that, test before and after a mitigation system is installed, test when you move into a new house, and test if the neighbors have found high levels, since the geology under a street is shared.

What you need

  • A radon test kit, a short-term one for a first look, or a long-term one left for months for a steadier reading, with the lab fee included or paid at mailing

Steps at a glance

  1. Buy a kit from a hardware store, the state radon program, or online, and check that the lab fee is included.
  2. Pick the lowest level of the house that people use, and a room away from the kitchen, bathrooms and drafts.
  3. Close the windows and outside doors for the time the kit's instructions specify before and during the test, which is why winter works best.
  4. Open the kit, set it on a surface away from walls and at breathing height, and note the start time.
  5. Leave it undisturbed for the test period, then seal it and mail it the same day.
  6. Read the result against the action level the lab reports, and keep the report with the house records.

You're done when the lab result is back and either below the action level or in hand for a mitigation contractor.

Signs it's overdue

  • The home has never been tested, which is most homes.
  • The neighbors have tested high.
  • You've finished the basement, or started spending time in it.

DIY or pro

This is an easy job, and the kit does the work. The short-term kit gives a first answer in days; a long-term kit, left for months, averages out the swings between seasons and is the better measure of what the house is really like. If a short-term test comes back high, run a second test or a long-term one before deciding on mitigation.

A professional test costs $150 to $300 and uses a continuous monitor that records the level hour by hour and can't be tampered with, which is why it's the test used in a home sale. A radon mitigation contractor is the next call if the level is high, and the system they install is a separate cost well above the test.

FAQ

How often should a house be tested for radon?

Every 2 years, and after any renovation, addition or finished basement. Levels change as the house and the ground beneath it change.

What time of year is best to test for radon?

Winter, when the house is closed up and the heating draws air up from the soil. Levels are usually highest then, which makes it the honest test.

How long does a radon test take?

A short-term kit sits for a few days before it's mailed. A long-term kit stays for months and gives a steadier average.

What if my radon test is high?

Confirm with a second test, then have a mitigation contractor install a system that vents the gas from under the slab. Test again after it's installed.