Does radon gas rise?

On its own, radon does not float upward the way a light gas would: it is far denser than nitrogen and oxygen.

Its weight is not what moves it into a home; the pressure difference is. See is radon heavier than air.

Radon levels are usually higher in basements, cellars and living spaces in contact with the ground, and are often higher in basements and lower levels. But considerable radon concentration can also be found above the ground floor, so an upstairs room is not automatically low.

Radon escapes from the ground into the air, where it decays and produces further radioactive particles. Indoors, its concentration varies considerably between neighboring buildings and, within one building, from day to day and hour to hour, so a reading from one floor on one day is a snapshot.

Testing is recommended for all homes below the third floor. The test goes in the lowest lived-in level: the basement if it is frequently used, otherwise the first floor. If you begin using a lower level, such as a basement, retest on that level.

Because radon comes up from below, the usual fix works where it enters. The method primarily used is a vent pipe and fan that pulls radon from beneath the house and vents it outside, preventing radon from entering from below the concrete floor and from outside the foundation.

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1. 1Soil gas drawn from beneath the slab
2. 2Suction point through the slab
3. 3Vent pipe
4. 4Fan, outside the living space
5. 5Discharge above the roofline