5 instruments, suitable for measuring environmental background gamma dose rates, have been assessed to determine their suitability for the task and ease of use in emergency situations such as those prevailing after the Chernobyl reactor accident. The selection of instruments for this evaluation has been influenced by those commonly used within the European Community for the task, but 1 relatively new instrument has also been included. In addition, an instrument developed to discriminate between variations in natural radiation and artificial gamma emitting radionuclides has been evaluated.

A comprehensive evaluation programme has been followed, which involved the instruments in field evaluation as well as the more common laboratory measurements, to allow the instruments to be assessed under realistic operating conditions.