This European Standard specifies constructional, functional, sizing, and testing requirements, also documentation and marking of gas safety shut-off devices: - for inlet pressures up to 100 bar and nominal diameters up to DN 400; - used at an operating temperature range from –20 °C to +60 °C which operate with fuel gases of the 1 st and 2 nd family according to EN 437 in transmission and distribution networks and industrial installations. For inlet pressures higher than 100 bar or nominal diameters DN > 400 or operating temperatures outside the range –20 °C to 60 °C, this standard can be considered as a guideline. Gas safety shut-off devices will hereafter be called SSDs except in titles. This European Standard considers the following classes of SSD: a) Temperature classes: - class 1: operating temperature range from –10 °C to 60 °C; - class 2: operating temperature range from –20 °C to 60 °C. b) Functional classes: - class A: SSDs that close when damage to the pressure sensing element occurs (applicable to overpressure SSDs only) or when external power fails; - class B: SSDs that do not close when damage to the pressure sensing element occurs or are able to be opened automatically by the pressure control system (applicable to overpressure SSDs only). NOTE 1 Some countries or purchasers can restrict the use of some of the classes listed above. NOTE 2 SSDs complying with the requirements of this standard can be declared as “in conformity with EN....“. The material and functional requirements specified in this standard are applicable to SSDs which use thermal energy or the effects of electrical energy to trip the operation of the closing member. For these SSDs the operational parameters are not specified in this standard.