According to the Pressure Equipment Directive 97/23/EU, a temporary excess pressure must be limited to 10% of the maximum permissible pressure.

Normal safety valves achieve the stroke necessary to release the required volume after being triggered within a pressure increase of maximum 10%.
After triggering by a pressure increase of within 5%, full-stroke safety valves open suddenly to the constructive limit of their stroke. The proportion of the stroke up to sudden opening must not exceed 20% of the total stroke. (See also DIN ISO 4126-1:2004, AD 2000 data sheet A2, ASME Code Sec. VIII Div I; UG-125 (c) )

According to AD 2000 data sheet A2 and DIN ISO 4126-1:2004, safety valves must close within a pressure reduction below the triggering pressure of 10% for compressible media and 20% for incompressible media.