What classification is NOT suitable for an electric fire?

The classification that is unsuitable for an electric fire is Class A. Class A fires involve ordinary combustible materials such as wood, paper, and cloth. These materials do not include electrical equipment or wiring, which are the primary concerns with electric fires.

Class C fires specifically address flammable gases and liquids that involve electrical equipment. When dealing with electrical fires, it is crucial to use extinguishing agents that do not conduct electricity, which is why Class C fire extinguishers are designed for that purpose.

By distinguishing the classifications, it's important to recognize that using water or foam, which is how Class A fires are typically extinguished, could pose a significant hazard on an electric fire by conducting electricity and increasing the risk of electrical shock or further igniting the fire. Hence, resorting to Class A for electrical fires is inappropriate and unsafe.