Which extinguisher should never be used on electrical fires?

Water should never be used on electrical fires because it is a conductive liquid. When water comes into contact with electrical equipment or live wires, it can conduct electricity, posing a significant risk of electric shock to the person using the extinguisher. This is particularly dangerous as it can lead to serious injury or even death.

In contrast, dry chemical, foam, and carbon dioxide extinguishers are safe and effective for use on electrical fires. These types of extinguishers work by interrupting the chemical reaction of the fire or displacing oxygen, thus extinguishing the flames without risking electrical conduction. Therefore, using water to extinguish an electrical fire is highly inadvisable and can result in catastrophic consequences.