A radon report is most useful when you read the number together with the test duration, location, and conditions. This guide explains indoor-air results for U.S. homes. It does not turn a home measurement into a medical diagnosis or replace the measurement professional’s interpretation.
What does pCi/L mean?
Picocuries per liter, written pCi/L, describe radioactive activity in a volume of air. Some devices instead display becquerels per cubic meter, written Bq/m³. These are two units for concentration, not different kinds of radon. EPA commonly presents 4 pCi/L as approximately 150 Bq/m³. [3]
Check the units before comparing devices or reading a threshold chart. A display of 148 Bq/m³ is about 4 pCi/L, not 148 pCi/L. The conversion is 1 pCi/L = 37 Bq/m³; regulatory guidance often rounds the equivalent action level. [4]
How should you interpret the result?
| Reported level | What it means | Next step |
|---|---|---|
| Below 2 pCi/L | Lower exposure, but no known risk-free level. | Keep the report and revisit testing when the home or its use changes. |
| 2 to below 4 pCi/L | Below EPA’s action level; reduction is still worth considering. | Discuss reduction options and whether additional measurement would inform the decision. |
| 4 pCi/L or higher | At or above EPA’s recommended action level. | Arrange the appropriate follow-up and mitigation when indicated. |
The thresholds above summarize EPA guidance. [1] A report of 3.9 pCi/L should not be treated as categorically harmless while 4.0 is treated as a completely different situation. The goal is to reduce exposure, not to win a pass/fail label.
What if your first short-term test is high?
EPA’s homeowner guidance uses a follow-up measurement to support the mitigation decision. A long-term result at or above 4 pCi/L, or an average of two appropriate short-term tests at or above that level, supports fixing the home. A much higher initial result calls for prompt follow-up rather than waiting months. [2]
Ask the tester three specific questions: Was this an initial screen or a completed decision protocol? Is the reported number the relevant average? What follow-up is appropriate for this result and deadline? A real-estate measurement may follow a protocol that differs from a casual home screening, so avoid adding arbitrary consumer readings to a professional report.
Do not average unrelated rooms, mismatched units, or a single hourly reading with a multi-day result. First confirm that the measurements belong in the same decision process. Save the original reports so a qualified tester can review them.
Why do radon readings change?
Radon levels can vary with time and season. A short test captures a limited period, while a longer measurement better represents a longer stretch of occupancy. [5] A monitor’s current, daily, and long-term averages can therefore differ without being contradictory.
When comparing results, write down the room and floor, dates, duration, units, device, and whether the radon system was operating. This small record helps distinguish a change in the home from a change in how the measurement was taken.
Does a high result mean you are already ill?
No home radon test diagnoses disease or measures an individual’s past dose. Radon is a long-term lung cancer risk; smoking increases the combined risk. Discuss personal health concerns with a clinician while addressing the building’s exposure source. [6]
What happens after the decision to mitigate?
Arrange a qualified assessment, get a written scope, and plan verification testing. Our guide to how radon mitigation works explains the basic system. You can also review Radon Eraser’s mitigation service or ongoing monitoring options.
If you later start using a basement as living space or alter the home, reassess the testing plan. EPA specifically identifies changed lower-level occupancy and renovations as reasons to revisit previous measurements. [7]
Radon result FAQs
Is 4 pCi/L a safe radon level?
No. It is EPA’s recommended action level. EPA says there is no known safe level of radon exposure and advises considering reduction between 2 and 4 pCi/L. [1]
Can I ignore a high hourly reading?
Do not base the entire decision on one hour. Check the device instructions, the appropriate measurement period, and the reported average; seek professional interpretation when readings remain elevated or the report is unclear.
Does a low result last forever?
No result describes every future condition. Keep it as a dated measurement and reconsider testing after meaningful changes to the home or where you spend time. [7]
Do Tennessee, Georgia, and Alabama use different units?
The units describe the same physical measurement wherever the home is located. Check your report’s units and consult the appropriate state radon program for local testing requirements rather than assuming a different health threshold from a city name.
Bring the whole report
For help choosing a practical next step, contact Radon Eraser with the report, measurement dates, and property location. Visit our locations hub to explore the communities we serve.