EPA Testing Recommendations
Based on EPA’s national testing guidance.
When a short‑term test is 4.0 pCi/L or higher
A single radon test is only a snapshot. Levels naturally rise and fall, so when your first short‑term test is 4.0 pCi/L or above, the next step is to confirm the result with a follow‑up test. This approach reflects EPA’s national homeowner testing guidance and is used across the U.S. for deciding when mitigation is needed.¹
Step 1 — Start with a short‑term test
Most homeowners begin with a short‑term test placed in the lowest lived‑in level of the home. If the result is 4.0 pCi/L or higher, move to Step 2.
Step 2 — Choose the right follow‑up test
You have two valid options, depending on how quickly you need clarity:
- Long‑term test — Measures radon across seasons and gives the best picture of your year‑round average.
- Second short‑term test — Useful when you need results quickly or when your first result was well above 4.0 pCi/L.
Higher initial results increase the likelihood that a second short‑term test is the appropriate follow‑up. This mirrors the logic used in national radon testing protocols.¹
Step 3 — Decide whether to fix your home
Your decision depends on which follow‑up test you used:
- If you used a long‑term test: Mitigation is recommended when the long‑term result is 4.0 pCi/L or higher.
- If you used two short‑term tests: Mitigation is recommended when the average of the two results is 4.0 pCi/L or higher.
These thresholds match widely accepted radon guidance and reflect the point at which radon exposure becomes a meaningful long‑term health risk.¹
Based on EPA’s homeowner testing recommendations, summarized from the brochure linked here: A Citizen’s Guide to Radon (PDF). 1