Class C
Fires involve electrical equipment. Thus, electricity is always present. It is often combined with combustible materials. An additional hazard of a Class C fire is the potential for electric shock while fighting the fire. If possible, always turn off the source of electricity before fighting an electrical fire. The fire may be extinguished, but if the electricity is not turned off, the fire may rekindle. (Class C fires deal with electrical Current.)
A Class C fire is extinguished with a dry chemical, which does not conduct electricity. The chemical is a very fine powder that smothers the fire when applied. A disadvantage is the mess the chemical makes when ejected from the extinguisher. Avoid breathing dry chemical extinguisher powder. Class C extinguishers may be used to extinguish Class A, Class B, and Class C fires. A Class C fire extinguisher is marked with a blue circle containing the letter C.
Class B is liquid fuel and Class C is gaseous fuel , as per ISO . Electrical is not considered as a class of fire but as a source of ignition.
As per NFPA (only American) class B is considered as liq/gas and class C as electrical.