Closed-house question · source-linked
Can You Open Windows During a Radon Test?
Learn when windows must stay closed during a short-term radon test, what normal entry means, and what to record if a window was opened.
Direct answer
For a short-term real-estate radon test, keep windows closed during the test and begin closed-house conditions at least 12 hours before a 2–4 day test. Normal brief entry through exterior doors is allowed; opening windows for ventilation is not.
Reviewed September 5, 2026. United States federal guidance. Device instructions and applicable state requirements take precedence.
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Reviewed September 5, 2026 · maintained by RadonVerdict.
The rule depends on the test you are running
EPA's home-sale checklist applies closed-house conditions to short-term transaction measurements. For a 2–4 day test, those conditions begin at least 12 hours before deployment and continue until the device is collected.
A long-term test is intended to represent normal living over many months. Do not automatically impose a short transaction protocol on it; follow the device and laboratory instructions for that measurement.
Normal entry is different from ventilation
Closed-house conditions do not require an empty or hermetically sealed building. EPA allows normal entry and exit through exterior doors, provided doors are not left open to exchange indoor and outdoor air.
Tell every occupant what the test requires before it starts. A written note near frequently used doors and windows is easier to follow than relying on memory.
If a window was opened, preserve the facts
Close the window when the mistake is discovered and record which window was open, approximately how long it stayed open, and when the event occurred within the exposure period.
Do not quietly erase the event or declare the result invalid from one fact alone. The device provider, laboratory, tester, or controlling transaction protocol should decide whether the measurement remains reportable.
Prevent the problem before deployment
Choose a period when the household can realistically maintain the required conditions. Avoid starting just before cleaning, moving, painting, construction, or an event that will keep doors open.
Record the pre-test start time separately from the device start time. That distinction makes the 12-hour preparation period reviewable later.
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Open the full test plannerCommon questions
Quick answers
Does opening a door ruin a radon test?
Normal brief entry and exit is allowed under EPA's closed-house definition. Leaving a door open for ventilation is a different condition and should be documented.
What if a window was open for five minutes?
Close it, record the event, and ask the device provider or tester whether the applicable protocol requires a retest. RadonVerdict does not invent a universal grace period.
Do windows stay closed for a long-term test?
Long-term tests are generally intended to reflect normal living. Follow that device's instructions instead of carrying over a short-term real-estate rule.
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