Radon Levels Chart: What Your Test Result Means

Before acting on a number from a dashboard or report

Check what the displayed value represents and keep short snapshots separate from a completed test result. If two devices or reports differ, compare their timing, locations and methods before drawing conclusions. Follow-up decisions should be based on appropriate measurement guidance rather than the most reassuring number.

• Confirm that the value and units are recorded correctly and identify the measurement period.
• Check whether the result is a completed test, a running average or an instantaneous display.
• Discuss the next measurement or mitigation step using the complete report and the home’s current use.

For the wider decision, read Should I Use a Radon Test Kit or a Professional in St. Louis?.

What radon level is dangerous?

Radon risk does not begin at one sharp boundary. EPA’s action level is a practical trigger for reducing exposure, not a line dividing harmless air from harmful air. Use the complete report and an appropriate follow-up plan instead of making a decision from a single unexplained number.

• Below 2 pCi/L: retain the result and consider changes in future home use.
• 2 to below 4 pCi/L: EPA says to consider reduction.
• 4 pCi/L or higher: EPA recommends fixing the home.

What is a good radon level?

A good radon result is a lower measured concentration supported by a valid test. Do not label a property permanently safe from one reading. The device, room, test dates and conditions explain what that reading represents.

When comparing reports, put the measurement details beside each number. A short-term basement result and a longer test in another room are not interchangeable simply because both use pCi/L. Ask the tester to explain any apparent disagreement.

• Compare the same units.
• Note the room and level tested.
• Keep the exposure dates with the result.

What does 4.0 pCi/L mean?

The unit pCi/L means picocuries per liter of air, a measure of radon’s radioactive activity in an air volume. A result of 4.0 pCi/L is the EPA action level. It does not describe a symptom, the age of the building or the visible condition of the foundation.

Make sure you are reading the reported test result rather than a peak value, device status indicator or a different air-quality metric. If a display uses another unit, ask for help interpreting it before comparing thresholds.

What should you do after a high radon test result?

After a high radon result, establish whether the measurement was valid and which follow-up action fits the test. CDC describes confirmatory testing after an elevated short-term screen and mitigation when the appropriate result remains elevated. A transaction can have its own required procedure.

Contact Air Sense with the complete report. Explain the intended use of the tested space, whether the building already has a system and whether any deadline applies. Keep the original measurement rather than replacing it with an informal summary.

• Confirm device, dates and location.
• Report testing-condition problems.
• Discuss the appropriate confirmation or mitigation step.
• Retain the follow-up report.

How common are high radon levels in St. Louis?

A St. Louis address needs its own measurement; this guide does not assign a local failure percentage without a verified dataset. Missouri DHSS links to residential testing maps, which can provide regional context. They do not measure an untested home.

When reading a map, look for its date range, geographic unit and explanation of the samples. A collection of voluntarily submitted tests is not automatically a random sample of every house. Do not compare two neighborhoods without checking what the map is actually counting.

• EPA action guidance: helps interpret an individual measurement.
• Missouri testing map: provides regional testing context.
• Your household report: records the tested property and period.