ISO 4126-1:2013 specifies general requirements for safety valves irrespective of the fluid for which they are designed.

It is applicable to safety valves having a flow diameter of 4 mm and above which are for use at set pressures of 0,1 bar gauge and above. No limitation is placed on temperature.

ISO 4126-1:2013 is a product standard and is not applicable to applications of safety valves.