This document specifies the minimum requirements for the protection of helium cryostats against excessive pressure, including the specific risks associated with cryostats for superconducting magnets and cryostats for superconducting radio-frequency cavities, coldboxes of helium refrigerators and liquefiers as well as helium distribution systems including valve boxes. It includes risk assessment, protection concepts, dimensioning of pressure relief devices, types of pressure relief devices, substance release and operation of helium cryostats. In order to fulfil the aim of this document, the characteristics of pressure relief devices are taken into account.