The purpose of this International Standard is to establish thefollowing characteristics for radionuclide gauges designed forpermanent installation : a) a classification of the gauges and shielding devices; b) technical construction and performance requirementsfor radiation protection when using a radioactive source; c) control and test methods to verify the compliance ofthe gauges with those requirements; d) indications to be shown on the gauges. In addition to the construction requirements above, the gaugesshall comply with existing regulations. This International Standard does not apply to gauges which,because of their design, and due to the nature and the low ac-tivityof the sources they contain, are not subject to generalrules regarding supply and possession of artificial radionuclidesnor does it apply to ion generators (smoke detectors, staticeliminators, etc.).