There exist the different conditions between the actual appliance and test conditions, such as,
 A. Fuse-holder
 B. Connecting cable size.
 C. Contacting resistance between fuse clip and fuse, etc.
 The above factors should be taken into consideration when selecting a fuse in a 25℃ ambient.  To compensate for the variation, the following conditions shall be melted to ensure the fuse operating continuously and properly.
 Fuse designed to IEC standard: current rating (In)=steady state current of circuit/0.9
 Fuse designed to UL standard: current rating (In)=steady state current of circuit/0.75

 The current carrying capacity tests of a fuse are performed at 25℃ and will be effected by changes with the ambient temperature. The higher the ambient temperature is, the shorter fuse life will be, and the lower the current carrying capacity will be. So the ambient temperature shall be considered for proper fuse selection. Refer to the following charts showing the effect on the current carrying capacity of all kinds of fuse.