If you are monitoring occupational dose to employees in a room where the source is located, or a room near a source that radiation could potentially reach, an Area Dosimeter Monitor should be placed at the highest exposure level where an employee may be working. Never place an Area Monitor on top of a source, or in a high radiation area that would not reflect occupational exposure.
It is the responsibility of the company to prove that the public is not being exposed to more than 100 mrem/year from outside a room/building. If you are monitoring potential exposure to the public, the Area Monitor should be placed on the outside of the room at the highest exposure level where employees/people are walking, sitting, or may have access.