ResourcesGlossary: testing
Closed-building conditions
Short answer
Closed-building conditions, also called closed-house conditions, mean keeping all windows closed, keeping doors closed except for normal entry and exit, and not operating fans or other machines that bring in air from outside while a short-term radon test runs.
What closed-building conditions means
EPA says that for a test of 2 to 4 days the conditions start at least 12 hours before the test begins and hold for the entire test period.
They are not optional. EPA says interference with the test or with closed-house conditions will invalidate the test result.
How long the house stays closed
Each row adds EPA's 12-hour lead-in to the hours of the test.
| Test length | Hours of testing | Lead-in, hours | Total hours closed |
|---|---|---|---|
| 2 days | 48 | 12 | 60 |
| 3 days | 72 | 12 | 84 |
| 4 days | 96 | 12 | 108 |
What it means for your home
Normal entry and exit is fine. What the rule stops is airing the house out while the test is running.
Weather counts too. EPA says not to run
Where to go next
- Which radon test to use. Pick the test first; the conditions apply to the short ones.
- What can affect a radon test. Open windows, weather, placement and the other things that move a result.