This part of IEC 60761 is applicable to equipment intended for simultaneous, delayed or discrete sequential measurement of aerosols in gaseous effluents discharged into the environment. It is applicable to equipment designed to fulfill the following functions: ñ the measurement of the volumic activity (Bq/m3) of the aerosols in gaseous effluents and/or the released total activity of aerosols (Bq); ñ the actuation of an alarm signal when either a predetermined volumic activity or a predetermined total released activity of aerosols is exceeded. This equipment is intended for measurement over a wide range of activity, including very small quantities in the presence of a much larger natural background. The daughters of 222Rn (radon) and 220Rn (thoron) are naturally occurring aerosols contributing to the natural background. The discrimination against natural activity can be an important problem in monitoring low level activity. In order to provide more and better information, complementary or retrospective laboratory analysis of the filters after collection may be performed. The object of this standard is to establish specific standard requirements, including technical characteristics and general test conditions, and to give examples of acceptable methods for aerosol effluent monitors. The general requirements, technical characteristics, test procedures, radiation characteristics, electrical, mechanical, safety and environmental characteristics are given in IEC 60761-1. Unless otherwise stated, these requirements apply to this standard.