This International Standard specifies the characteristics of reference sources of radioactive surface contamination, traceable to national measurement standards, for the calibration of surface contamination monitors. This International Standard relates to alpha-emitters, beta-emitters and photon emitters of maximum photon energy not greater than 1,5 MeV. It does not describe the procedures involved in the use of these reference sources for the calibration of surface contamination monitors. Such procedures are specified in lEC 60325, IEC 62363 and other documents. NOTE Since some of the proposed photon sources include filters, the photon sources are to be regarded as sources of photons of a particular energy range and not as sources of a particular radionuclide. For example, a 241Am source with the recommended filtration does not emit the alpha particles or characteristic low-energy L X-ray photons associated with the decay of the nuclide. It is designed to be a source that emits photons with an average energy of approximately 60 keV. This International Standard specifies also reference radiation for the calibration of surface contamination monitors, which takes the form of adequately characterized large area sources specified, without exception, in terms of surface emission rates, the evaluation of these quantities being traceable to national standards.