This standard specifies the requirements for the design, manufacture and testing of safety valves for cryogenic service i.e. for operation with cryogenic fluids below – 10°C in addition to operation at ambient temperature. It is a requirement of this standard that the valves comply with prEN ISO 4126-1:2001. In the event of different requirements, this standard takes precedence over that standard. This standard is restricted to valves not exceeding a size of DN 100 designed to relieve single phase vapours or gases. A valve can be specified, constructed and tested such that it is suitable for use with more than one gas or with mixtures of gases.