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.
Questions before you book
Does a low result in another room cancel a high result?
No. Review the location and purpose of both tests with a qualified tester. Keep both reports so the difference can be interpreted.
Can I compare an hourly spike with the action level?
Use the reported result and applicable protocol for the decision. Ask the tester how any time-series readings relate to the final measurement.
Should I send only the final number when requesting help?
Send the full report if possible. Duration, location, units and conditions are needed to understand the number.