Which type of fire extinguisher should NOT be used on a fire in the MCC room at an electrical panel?

Using pressurized water on a fire in the MCC (Motor Control Center) room at an electrical panel is not appropriate due to the risk of electric shock and potential worsening of the fire. Water conducts electricity, and when sprayed on an electrical fire, it can create a path for the electricity to travel, possibly injuring the person trying to extinguish the fire and causing further electrical damage.

In contrast, carbon dioxide extinguishers are suitable for electrical fires as they work by displacing oxygen and do not conduct electricity. Dry chemical extinguishers also effectively put out electrical fires and prevent re-ignition. Foam extinguishers, while mainly used for flammable liquid fires, can sometimes be suitable for certain types of electrical fires but are generally less preferred compared to CO2 or dry chemical types in an electrical setting.