What is the primary agent used to extinguish energized Charlie fires?

The primary agent used to extinguish energized Charlie fires, which involve burning materials such as metals (specifically, certain types of metals like magnesium, sodium, and potassium), is carbon dioxide (CO2). Carbon dioxide is effective because it displaces oxygen in the vicinity of the fire, thus smothering the flames without the potential reactivity that other agents might present.

When dealing with energized electrical fires, the properties of the extinguishing agent are crucial; CO2 is non-conductive, which makes it a safe choice for use around energized equipment. It also does not leave a residue that can cause further problems, making it suitable for environments where minimizing contamination is important, such as in aircraft or electronic equipment.

In contrast, other agents may not be effective or safe for these types of fires. For instance, using water—whether in high velocity fog or otherwise—on a Charlie fire can be dangerous as it can react explosively with certain metals. Aqueous film forming foam and dry chemical powders have their roles in firefighting but are typically not preferred for class Charlie fires involving energized equipment due to their potential reactivity and the risks associated with electrical hazards.