How to Read Your Radon Test Results
You mailed back the kit and got an email from the lab. There is a number on the report, measured in pCi/L. Now what?
This guide explains what the number means, what the EPA recommends at each level, and what Tipper would actually do if he got each result. No jargon, no panic, just a clear read on where you stand.
What pCi/L actually means
pCi/L stands for picocuries per liter. A picocurie is a unit of radioactivity, one trillionth of a curie. In practical terms, the number tells you how much radon is in each liter of air inside your home.
You do not need to understand the physics. What matters is where your number falls relative to two benchmarks: the EPA action level of 4 pCi/L, and the national average of 1.3 pCi/L. Your lab report gives you one number. The chart below tells you what to do with it.
What your result means
Well below the EPA action level.
No action needed. You are in good shape. Retest every two years or after major foundation work.
Below the action level, but above the national average.
Consider a follow-up long-term test (90+ days) for a more accurate seasonal picture. Mitigation is optional but reasonable, especially in rooms where people sleep.
At or above the EPA action level. Fix your home.
Confirm with a long-term test, then contact a certified mitigation contractor. Systems typically cost $800–$2,000 and bring levels well below 2 pCi/L.
Significantly elevated. Act promptly.
Skip the confirmation test. Contact a certified contractor and schedule mitigation. At this level, the benefit of a long-term average is not worth the wait.
Why 4 pCi/L?
Putting your number in context
A single number on a lab report does not exist in a vacuum. Here are a few things worth knowing when you interpret your result:
- •Short-term tests are snapshots. A 48-hour reading captures conditions during those two days: weather, barometric pressure, ventilation, and season all affect the number. A long-term test (90+ days) gives you a much better annual average.
- •Radon fluctuates. Levels are typically higher in winter when homes are sealed up and lower in summer when windows are open. A high winter reading does not mean your home is always that high. It does mean that is what your family breathes during the months you spend the most time indoors.
- •Lower floors read higher. Radon enters through the foundation, so basement and ground-floor readings are almost always higher than upper-floor readings. Test in the lowest livable area where people spend time.
- •Your neighbor's result tells you nothing. Two homes on the same street can differ by a factor of five depending on foundation type, soil, and construction. Your test result is the only one that matters.
Search your county on RadonLookup to see how your result compares to the county average and EPA zone. That is useful context, but remember that your home's number is what drives your decision.
What to do next
Your result tells you exactly one thing: whether you need to act. Here is the decision tree Tipper uses:
- •Below 2 pCi/L: You are done. Set a reminder to retest in two years.
- •2 to 4 pCi/L: Run a long-term test for a better annual average. If the long-term test also comes back above 2, consider mitigation, especially if anyone in the house smokes or sleeps on the lowest level.
- •4 to 8 pCi/L: Confirm with a long-term test. If it holds, hire a certified contractor.
- •Above 8 pCi/L: Call a contractor. A mitigation system will get you below 2 pCi/L. It is one of the most cost-effective health investments a homeowner can make.
If you tested during unusual conditions, such as an extreme cold snap, unusual wind, or renovation work, and the result is borderline (3 to 5 pCi/L), a second short-term test under more typical conditions is a reasonable step before committing to mitigation.