Which fire extinguisher should NOT be used in an electrical MCC room fire?

Using a pressurized water extinguisher in an electrical MCC (Motor Control Center) room fire is highly inadvisable due to the conductivity of water. Water can conduct electricity and, when applied to live electrical equipment or burning wiring, it poses a significant risk of electrocution to the person operating the extinguisher. Furthermore, introducing water into an area that may contain live electrical components could potentially exacerbate the situation, leading to further equipment damage or a more severe fire.

Effective alternatives for fighting electrical fires include dry powder extinguishers and carbon dioxide extinguishers. These types do not conduct electricity and are specifically designed for use in areas with electrical components. While foam extinguishers can be effective on various class A fires, they can create a similar danger as water when used on electrical fires, making a pressurized water extinguisher the least suitable option.