Choose a path
Speed and representativeness are different goals.
Short-term
EPA describes a short-term test as lasting from 2 to 90 days, depending on the device, and says all radon tests should run for at least 48 hours. This is the quicker route, but a short interval is less likely to represent a year-round average.
Long-term
A long-term measurement is more likely to reflect the home’s year-round average. Use it when the decision can wait and follow the device or laboratory instructions.
Real-estate testing uses a time-sensitive path with explicit interference controls. A qualified Florida measurement business can explain which current protocol applies to the transaction. Do not assume every DIY device or one continuous monitor is interchangeable.
Closed-house conditions
Keep the test conditions stable and documented.
For a 2–4 day short-term test, EPA says to keep windows and exterior doors closed for at least 12 hours before the test and throughout it, except for normal entry and exit. For 4–7 day tests, EPA recommends maintaining closed-house conditions.
- Operate heating and cooling normally; for tests shorter than one week, use only air-conditioning that recirculates indoor air.
- Do not operate fans or machines that bring outside air indoors. Briefly used small exhaust fans and an existing radon-system fan may operate.
- Do not move or disturb the device.
- Avoid starting a test shorter than four days during severe storms or high winds.
Device placement
Follow the device first, then check the basics.
EPA’s buyer and seller guide says a short-term device should be at least 20 inches above the floor, where it will not be disturbed, and away from drafts, high heat, high humidity and exterior walls. The device instructions may be more specific and should control.
Stable, undisturbed and separated from drafts, heat, humidity and exterior walls.
The complete record
Ask what the number is built from.
A useful report identifies the device or method, start and stop times, test location, conditions, result, and the certified business and individual when paid professional work is involved. For a transaction, ask how interference was prevented or detected.
In Florida, anyone charging for sampling, analysis or interpretation generally must be certified by the Department of Health. A property owner or occupant may perform a test under a statutory exemption, but the parties to a transaction can require a qualified professional path.