How to Read a Radon Levels Chart
A radon levels chart compares a test result with an action level, but check the unit and the test period before drawing conclusions. In the United States, the EPA recommends taking action at 4 pCi/L or higher.
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A radon levels chart compares a test result with an action level, but check the unit and test period before drawing conclusions. In the United States, the EPA recommends taking action at 4 pCi/L or higher.
A chart is a guide to interpreting a measurement, not a guarantee about every room or every day. First find the reported number, its unit, and whether the test was short-term or long-term.
How do you read a radon levels chart?
Match your result to the chart's unit, then compare it with the action level shown. A result in pCi/L cannot be compared directly with a number in Bq/m³ until you convert the units.
In the United States, results are commonly reported in picocuries per liter (pCi/L). Many other countries use becquerels per cubic meter (Bq/m³).
Both describe radon concentration, but their numbers use different scales.
A chart may use color bands or labels such as low, raised, and action level. Read the chart's own key, since colors and descriptions are not universal standards.
The EPA recommends fixing a home if the result is 4 pCi/L or higher. It also advises considering a fix when results are between 2 and 4 pCi/L.
These are action guidelines, not a line where lower readings carry no risk.
For help understanding the full report, see how to read radon test results. If you haven't tested yet, how to check radon levels explains the basic process.
What do pCi/L and Bq/m³ mean on a radon gas levels chart?
pCi/L and Bq/m³ are two units for describing radon concentration. Convert between them before comparing a measurement with a chart that uses the other unit.
To get an approximate pCi/L value, divide Bq/m³ by 37. To get an approximate Bq/m³ value, multiply pCi/L by 37.
| pCi/L | Approximate Bq/m³ |
|---|---|
| 1 | 37 |
| 2 | 74 |
| 4 | 148 |
| 10 | 370 |
These conversions are rounded for easy reading. Use the unit printed on your test report, and follow any interpretation given by the lab or your local radon authority.
How do you convert a radon reading from Bq/m³ to pCi/L?
Divide the Bq/m³ number by 37 for an approximate pCi/L reading. For example, 185 Bq/m³ is about 5 pCi/L.
A conversion helps you compare units, but it doesn't make results from different tests directly interchangeable. Check when and where each sample was taken, and whether the test methods and durations match.
Why does the testing period matter on a radon chart?
A short-term result reflects a limited period, while a long-term result captures more variation over time. Always read the duration alongside the concentration.
Short-term tests are useful for screening and can help identify a potential issue quickly. However, radon levels can change with weather, ventilation, and how a home is used.
A reading from a few days does not describe every day of the year.
Long-term tests measure over more than 90 days and can give a better picture of average exposure in a home. Follow the test instructions and local guidance about which type of test to use and whether a follow-up is needed.
A chart that puts short-term and long-term results side by side may help you spot patterns, but don't assume they measure the same conditions. Compare measurements from the same location and note the start and end dates.
What does the EPA action level mean?
The EPA action level is 4 pCi/L, or about 148 Bq/m³. At or above that result, the EPA recommends taking steps to fix the home.
The action level is a decision point for reducing exposure. It does not mean readings below 4 pCi/L are risk-free, and it does not diagnose a health condition.
If your result is raised, follow the test provider's instructions and consult a qualified radon professional about confirmation and mitigation. The EPA's consumer guide to radon reduction describes what homeowners can do after testing.
For context on typical readings and the action threshold, read what normal radon levels in a home mean. Short-term results can also shift with conditions such as rain, as explained in whether radon levels are higher when it rains.
Does a lower chart category mean no risk?
No chart category can promise zero risk from radon. Lower concentrations generally mean lower exposure, but radon risk does not begin only at the action level.
Use the chart to decide whether more testing or action is appropriate. Don't stop testing solely because a result falls in a chart's lowest color band, especially if the test was short-term or the home has never been checked.
Which radon test kits can give you a chartable result?
A lab-analyzed test kit can provide a concentration you can compare with a radon chart. Follow its placement, exposure, and return instructions so the result reflects the intended test period.
The First Alert Radon Gas Test Kit includes test materials and lab fees, with results emailed within 72 hours of lab receipt.
The PRO-LAB Radon Test Kit for Home is a short-term test with a 48-hour collection period and lab analysis included.
The Leaping Lynx Radon Test Kit for Home uses a 48-hour short-term collection period and includes lab analysis; postage is required to return the detector.
Before testing, check that the kit is suitable for your location and follow its instructions for room placement and exposure time. A kit's result is useful only when you interpret it in the correct unit and alongside its testing period.
What should you do after reading a radon chart?
If a result is 4 pCi/L or higher, follow up with testing guidance and consider a qualified mitigation professional. If the result is lower but close to that level, consider the EPA's advice and your local rules.
Keep the original report. Record the room, test dates, unit, and whether the test was short-term or long-term.
Those details make it easier to compare later results.
If two results differ, don't average them casually or treat a single chart as the final answer. Check whether the same room, method, and test duration were used, then ask the lab or a qualified professional how to proceed.
When comparing any radon levels chart, start with the unit, check the test period, and use the EPA action level as a guide. Choose a follow-up test or professional advice based on the result and the conditions in your home.
Frequently asked questions
What is a safe radon level?
There is no known risk-free level of radon, but the EPA recommends fixing a home at 4 pCi/L or higher. Consider reducing radon when results are between 2 and 4 pCi/L.
Follow local guidance, and use a qualified professional to discuss mitigation options.
How do you convert Bq/m³ to pCi/L?
Divide Bq/m³ by 37 to get an approximate result in pCi/L. For example, 148 Bq/m³ is about 4 pCi/L.
Use the conversion only to compare units; it does not change what the original test measured or replace the lab's interpretation.
Is a short-term radon test enough?
A short-term test gives a snapshot over its stated testing period, so results can vary with weather, ventilation, and other conditions. If it shows a raised result, follow the test instructions and EPA guidance about confirming it with a second test or a long-term test.
What does 4 pCi/L mean on a radon chart?
Four pCi/L is the EPA action level for radon in homes in the United States. It is a level at which the EPA recommends taking action to reduce radon, not a boundary between safe and dangerous air.
A qualified radon professional can explain mitigation choices.
