You can't see or smell it. But one simple test can tell you if it's in your home.
7 min read
Radon is the second leading cause of lung cancer in the U.S., and the leading cause in people who never smoked.
The EPA estimates radon causes about 21,000 lung cancer deaths a year. It's a radioactive gas that comes up from the soil and can seep into any home, old or new. You can't see, smell or taste it. Test kits are inexpensive, and a high result can be fixed.
Radon is the one item in this guide where the whole fix is a single test. Roughly 1 in 15 U.S. homes is estimated to have elevated radon.
The risk is much higher when radon and smoking combine: the American Lung Association says that for people who smoke, the risk of radon-related lung cancer increases about 10 times. But radon isn't only a smoker's problem. The EPA estimates that at 4 pCi/L over a lifetime, about 62 of every 1,000 smokers would get lung cancer, and about 7 of every 1,000 never-smokers.
The EPA says nearly two million homes with high levels have already been fixed.
21,000
lung cancer deaths a year are linked to radon
EPA
1 in 15
U.S. homes is estimated to have elevated radon
EPA, A Citizen's Guide to Radon
4 pCi/L
is the level where the EPA recommends fixing your home
EPA
62 vs 7
estimated lung cancer cases per 1,000 smokers vs. never-smokers over a lifetime at 4 pCi/L
EPA
1. Get a kit
Order a short-term kit online or pick one up at a hardware store. Choose a kit analyzed by a qualified laboratory, and follow its instructions. Short-term tests run 2 to 90 days depending on the device.
2. Pick the spot
Place it in the lowest lived-in level (the basement if you use it often, otherwise the first floor), in a regularly used room that isn't the kitchen or bathroom. Keep it at least 20 inches above the floor and away from drafts, heat, humidity and exterior walls.
3. Keep the house closed
Keep windows closed and exterior doors shut except for normal coming and going. Don't run fans or equipment that bring in outside air. For tests shorter than four days, keep the house closed for at least 12 hours before you start and during the test. Avoid starting during a severe storm or high winds.
4. Mail it right away
Reseal the package and send it to the lab as soon as the test period ends. Results usually arrive within a few weeks.
| Your result | What the EPA says |
|---|---|
| Under 4 pCi/L | Below the action level, though the EPA notes levels below 4 still carry some risk. The average indoor level is about 1.3 pCi/L. |
| 4 to under 10 pCi/L on a short-term test | Follow up with a long-term test or a second short-term test. |
| 10 pCi/L or higher on a short-term test | Take a second short-term test right away. |
| Long-term follow-up of 4 or higher | Fix your home. |
| Average of two short-term tests is 4 or higher | Consider fixing your home. |
The most common fix is a soil suction system. A vent pipe and fan pull radon from beneath the house and vent it outside, and sealing cracks improves it. The EPA says most homes can be fixed for about the same cost as other common home repairs, though costs vary widely.
Hire a contractor trained or certified in radon mitigation, and get multiple estimates. If your result is high, contact your state radon program, which can point you to qualified professionals. Some states offer financial help or low-interest loans.
Retest after any fix to make sure it's working. Retest if you start using a lower level of the home, like a finished basement. Even if your result was under 4, consider testing again sometime in the future, especially after major renovations. Test any home you're buying.
Myth
Radon only affects smokers.
What research says
It's the leading cause of lung cancer in people who never smoked. Smoking multiplies the risk, but never-smokers are not exempt.
EPA; American Lung Association
Myth
A high result means you have to move.
What research says
Radon can be reduced with a vent-and-fan system, and nearly two million homes with high levels have been repaired.
EPA
Myth
Testing is expensive and complicated.
What research says
The EPA calls testing inexpensive and easy. Do-it-yourself kits are sold at home improvement stores and online.
EPA
Myth
Newer homes don't have radon problems.
What research says
Radon can seep into any home, old or new, whatever the foundation. The only way to know your level is to test.
EPA
Myth
Below 4 means zero risk.
What research says
The EPA says levels below 4 pCi/L still pose some risk, and suggests considering action between 2 and 4.
EPA; American Lung Association
Order a kit today
Get a short-term kit and put the delivery date on your calendar.
Place it the day it arrives
Follow the placement and closed-house rules above and mail it back the same day the test ends.
Calendar the result
Mark the date results should arrive. If you're at 4 or higher, plan your follow-up test or contact your state radon program.
Set a reminder to retest
Retest after any fix or move to a lower level of the home, and consider testing again from time to time.
- U.S. Environmental Protection Agency: A Citizen's Guide to Radon
- U.S. Environmental Protection Agency: Prevent lung cancer by testing your home for radon (news release)
- American Lung Association: Radon fact sheet, January 2025