Only B/c extinguishers containing the dry chemicals sodium bicarbonate or potassium bicarbonate should be used on what type of fire?
B C extinguishers are to be used on flammable liquids (B), and electrical equipment (C).
The B in BC extinguishers means they are specifically used on fires involving flammable liquids, such as oil, gasoline, kerosene or paint that occur in the kitchen (or laboratory), or in a vehicle.
The C in BC fire extinguishers means they are used on electrical fires, such as might occur with an electrical burner, hot plate, or computer equipment.
Class B and C fire extinguishers are designed primarily for flammable liquids (Class B) and electrical fires (Class C).
The chemical reason for the designations is the ability of the compounds to decompose into carbon dioxide to smother a fire without either causing splashing (liquids) or reactivity (electrical) that would occur with a water fire extinguisher. Other suitable compounds used in these Classes are carbon dioxide, Halon (discontinued) and foam.
Both may also be used for combustible solids (Class A), but may not be as effective as a Class A extinguisher. They should not be used for Class D (flammable metals). NOTE that the CODE CLASSES are slightly different in the UK with more subdivisions.
The UK Code is here: