What does a 4.0 pCi/L radon result mean?

It reaches EPA's action level. A first short-term result needs a follow-up test; an average of two short-term tests or a long-term result at or above 4.0 pCi/L supports contacting a licensed radon-reduction professional.

What does a radon result between 2.0 and 4.0 pCi/L mean?

EPA and CDC say homeowners should consider reducing radon in this range. Keep the test type and procedure with the reading because a short snapshot and a long-term result provide different context.

Can I average two short-term radon tests?

CDC says to calculate the average when the follow-up is a second short-term test. If that average is at or above 4.0 pCi/L, contact a licensed professional about reduction.

Does a low county average override my home result?

No. County and zone data are context only. Testing is the only way to know the radon level measured in a particular home.

Report-first decision tool

What does my radon test result mean?

The number matters. The test type and procedure determine what that number can support next.

Your test record

Enter what the report actually says

Nothing is uploaded or saved. Unknown is a valid answer; the tool will keep the missing fact visible.

1. Reported result Radon reading, pCi/L

2. Test type

First short-term test2–90 day measurement; follow-up may be needed. Two short-term testsThe tool will calculate their average. Long-term testMore than 90 days. After mitigationChecks an installed system. I cannot identify the test typeThe report, laboratory, or tester may identify it.

3. Procedure record Decision context

Recorded interpretation

Complete the record

04.0 EPA action level8+

No reading entered

The procedure check comes before the next-step guidance.

Read the sequence, not only the band

What the national guidance says

Below 2.0 pCi/L: CDC lists no immediate action, while EPA says no radon level is risk-free. Keep the report and retest when lower-level occupancy or major building changes alter the question.
2.0–3.9 pCi/L: EPA and CDC say to consider reducing radon. Test type, time coverage, and procedure still belong with the number.
First short-term ≥4.0: Take a second short- or long-term test. When the second is short-term, calculate the average of both results.
Confirmed or long-term ≥4.0: An average of two short-term tests or a long-term result at or above 4.0 supports contacting a licensed radon-reduction professional.

Important boundary

A county average cannot validate this result

County measurements and EPA zones can show why testing matters locally. They cannot replace the device report, prove the procedure was followed, or overturn a result from the home.

Use local data as context →

Transaction boundary

Do not turn one result into a price claim

For a purchase or sale, preserve the report, protocol, deadline, and written scope separately. A radon number does not determine a universal repair cost or seller credit.

Open the transaction decision guide →

Primary guidance

Sources used by the interpreter

Testing for Radon in Your HomeCDC · test types, result bands, follow-up tests, and reduction decisions EPA action level and what it meansU.S. EPA · 4.0 pCi/L action level and reduction below it How often should I retest?U.S. EPA · future testing, transactions, renovation, and lower-level occupancy

Reviewed September 5, 2026. This tool organizes published federal guidance; it does not diagnose health effects, validate a laboratory report, or replace state requirements and qualified professional judgment.