The fuses of devices that have been used for many years sometime suddenly blow and often metal fatigue is the cause. But why would a fuse with no moving parts be affected by metal fatigue? When the power is switched on, the inrush current instantly heats and expands the fuse. Later, the fuse returns to its original condition. This process repeats again and again, which causes wear over the years that may cause the fuse may blow.

Even with the same fuse, high ambient temperatures make a fuse more likely to blow. Higher temperatures lower the resistance value of the fuse, which makes heating and fusing more likely. Because of this characteristic, it is normal practice to select a fuse 1.5 to 3 times the rated current of the device used.