Controlled Area: Any area to which access is limited for any reason.  X-ray rooms and accelerator rooms are controlled administratively by the personnel who operate the equipment.  Laboratories using radioactive materials are controlled by posting and locking for the purpose of preventing unauthorized removal of these materials.  Exposure to radioactive materials is prevented by controlling the materials, and by limiting normal access to the laboratory when it is open and attended.
 

Very High Radiation Area: Any accessible area, in which radiation absorbed dose exceeds 500 rad in 1 hour at 1 meter (3.28 ft) from the source or from any surface the radiation penetrates. High Radiation Area:  Any accessible area in which an individual could receive a dose equivalent exceeding 100 mrem in 1 hour at 30 cm (1 ft) from the source or from any surface the radiation penetrates.

Typical high radiation area signs used at ISU

Radiation Area:  Any accessible area in which an individual could receive a dose equivalent exceeding 5 mrem in 1 hour at 30 cm (1 ft) from the source or from any surface the radiation penetrates.

Restricted Area: an area, access to which is limited for the purposes of protecting individuals against undue risks from exposure to radiation and radioactive materials.  It is an area that is defined by a responsible user to the purposes of working with radioactive materials.  An area must be posted as a Restricted Area if the dose rate is >2 mrem/hr or it contains > 0.02 ALI of dispersible radioactive material.  A Restricted Area will have some type of marked or physical boundary so that untrained personnel will be prevented from accessing the area.