What Is a Safe Radon Level?
Learn what radon levels mean, when the EPA says to act, how pCi/L compares to Bq/m³, and why lower is always better.
There is no level of radon that is known to be completely safe. Health agencies set guideline levels that tell you when to take action, but the lower your long-term exposure, the lower your risk.
Guideline levels
| Guideline | Level |
|---|---|
| U.S. EPA action level | 4 pCi/L (148 Bq/m³) |
| EPA “consider fixing” range | 2–4 pCi/L |
| WHO reference level | 100 Bq/m³ (≈ 2.7 pCi/L) |
pCi/L vs Bq/m³
The United States measures radon in picocuries per liter (pCi/L). Most other countries use becquerels per cubic meter (Bq/m³). One pCi/L equals 37 Bq/m³.
Why one reading isn’t enough
Radon levels rise and fall with weather, season and ventilation. A single short test can land on an unusually high or low day. Long-term or continuous monitoring shows your true average — which is what matters for health.
Frequently asked questions
Is 2 pCi/L of radon safe?
It is below the EPA action level, but the EPA still suggests considering mitigation between 2 and 4 pCi/L because risk rises with exposure.
How do I convert pCi/L to Bq/m³?
Multiply by 37. For example, 4 pCi/L equals 148 Bq/m³.
Sources
- Health Risk of Radon — U.S. EPA
- A Citizen's Guide to Radon — U.S. EPA
- Radon and health (fact sheet) — World Health Organization