The location of a radon test device depends upon whether the test is being done for a real estate transaction or not.
Since the purpose of the first, short-term test is to be able to identify homes that are clearly below 4.0 pCi/L, it is necessary to place the test device in a part of the home that would be expected to have the highest radon level.
The device should be placed in a room that is frequently occupied, but where high humidity in the air would not be expected. Examples of good locations would be bedrooms, dining rooms, and family rooms. Never place the device in a closet, crawlspace, storage area, kitchen, garage, or bathroom.
For non-real estate transactions the device should be placed in the lowest occupied space A finished basement is normally chosen in those parts of the country that typically have basements.In the case of a real estate transaction, the device should be placed in the lowest portion of the home that could be finished and occupied by future residents.
If the reading comes back below 4.0 pCi/L, there is good reason to believe that the rest of the home is also less than 4.0 pCi/L. Furthermore, if the closed-house test protocols are followed, there is good reason to believe that a low short-term test result (below 4.0 pCi/L) means that the average radon throughout the year will probably also be below 4.0 pCi/L, during normal use of the house.
Remember, short-term tests determine the radon potential of a home, independent of how future homeowners may operate or occupy the house.
3 feet from windows or exterior doors.
At least 20 inches above floor.
4 inches from other objects.
Where it won’t be disturbed.
Away from drafts.
Out of direct sunlight.
Not on hot or warm surfaces
A proper location must be selected to obtain an accurate measurement of radon in air that represents the breathing space of the home. The test device should be at least 20 inches from the floor, 4 inches from another object, 12 inches from an exterior wall, and 3 feet from an outside window. The device can be placed near an interior wall, perhaps on a bookshelf, but should be at least four inches from the wall or the back of the shelf to allow for good air circulation.
Devices that are designed to be hung by a string should be approximately 12 inches from the ceiling.
Test devices should also be located away from drafts and should not be placed in rooms with excess humidity.