ISO 4126-5:2013 specifies the requirements for controlled safety pressure relief systems (CSPRS) irrespective of the fluid for which they are designed. It is applicable for main valves having a flow diameter of 4 mm and above which are for use at pressures of 0,1 bar gauge and above. No limitation is placed on temperature. ISO 4126-5:2013 is a product standard and is not applicable to applications.