Glossary · Health & indoor air
Radon test (long-term vs short-term)
Also called: radon testing · long-term radon test · short-term radon test · radon test kit · radon detector · digital radon monitor
Measuring radon with a detector left in the home; long-term tests, over 90 days, give the most reliable yearly average.
What it means
Short-term tests last 2 to 90 days and give a quick snapshot, but radon rises and falls with weather and season. Long-term tests run more than 90 days and give a better picture of your yearly average. Place the detector in a regularly used room on the lowest lived-in level, away from kitchens, bathrooms, drafts and the floor.
Why it matters in an audit
Mitigation decisions should rest on a reliable average, and a retest after air sealing or a new HRV shows whether radon changed.
Typical numbers
Reference values with their sources. Your auditor’s report gives the figure for your own house.
| What | Value | Source |
|---|---|---|
| US EPA | Short-term 2–90 days; long-term over 90 days; if a short-term result is 4 pCi/L or more, follow up with a long-term or second short-term test; place the kit at least 20 inches above the floor | nepis.epa.gov ↗ |
In the United States
EPA's approach is a short-term test first, then a follow-up long-term or second short-term test before deciding to fix.