IEC 62533:2010 applies to hand-held instruments used for the detection and localization of radioactive photon emitting materials. These instruments are highly sensitive meaning that they are designed to detect slight variations in the range of usual photon background caused mainly by illicit trafficking or inadvertent movement of radioactive material. The object of this standard is to establish performance requirements including physical characteristics, general test conditions, radiation characteristics, electrical safety, and environmental conditions. This standard provides examples of acceptable test methods to determine if an instrument meets the requirements of this standard. The results of tests performed provide information to users on the capability of radiation detection instruments for reliably detecting photon sources.