This International Standard defines technical requirements for equipment for monitoring of alpha-, beta- or gamma-emitting radionuclides in liquid effluents and surface waters, provides some general guidance as to the possible detection capability of such equipment and indicates when and where its uses may be practicable. NOTE Alpha monitoring in liquids is a possibility that has been demonstrated using a concentration device and collection of the concentrate in a filter, so this standard may also be applicable to alpha monitoring in liquids. This standard is applicable to equipment for continuous monitoring of the activity: – in liquid effluents which could be released in the environment during normal operations; – in environmental waters. This standard does not apply to equipment specifically for use in accident conditions that may require additional capabilities. This standard is restricted to equipment for continuous monitoring of gross alpha or gross beta of maximum energy higher than 150 keV or gamma activity in liquid effluent streams and environmental waters. It does not deal with sample extraction and laboratory analysis. The object of this standard is to lay down general requirements and give examples of acceptable methods for equipment to monitor continuously the activity of water. This International Standard specifies, for the equipment described in the scope, the general characteristics, general test procedures, radiation, electrical, safety and environmental characteristics, and the identification and certification of the equipment. Performance requirements for the safe operation of electrical equipment are provided in IEC 61010-1. These safety requirements and corresponding tests are applicable if the manufacturer wants to, or is required to, label its equipment with the appropriate safety mark (for example, CE, UL, etc.). This standard is applicable to water monitors intended to fulfil the following functions: – measurement of the volumetric activity or count rate (see 5.1.2) due to radionuclides in the liquid and its variation with time; – actuation of an alarm when a limit value of volumetric activity or count rate in water is exceeded. Annex A gives some guidance for use with radioactive water monitors.