What is a fuse in a circuit?
Fuses are inherently safe but carry some risk. When there is an electrical overload in the circuit, the metal strip inside the fuse's cartridge melts and breaks the circuit. With your appliances now protected, you can replace the fuse. It is in that replacement that the risk appears.
If you touch the metal contacts of the fuse or panel, you could get shocked and injured. The other primary concern is using the wrong size fuse or something other than a fuse that still closes the circuit. This frequently happens, often by accident, and increases the risk of overheating wires, melting, fire, and damaged appliances.
To prevent issues, licensed electrical contractors (LECs) must now follow specific rules when working on fuse boxes. For example, LECs must install fuse rejectors if adding a circuit to a fuse box. As the name suggests, the rejector will refuse improper fuses or other items placed in the fuse's housing.
These risks have influenced insurance companies to require homeowners to upgrade their fuse boxes to breaker panels. Even though fuses provide sufficient electrical protection, the potential for user error makes them a less desirable choice to insure.