How do Class C extinguishing agents primarily differ from other types?

Class C extinguishing agents are specifically designed for use on fires involving energized electrical equipment, which can include wires, circuit breakers, and appliances. The primary difference between Class C agents and those of other classifications relates to their ability to safely extinguish fires without conducting electricity, thereby reducing the risk of electric shock to the firefighter or further ignition. This non-conductive property is crucial because traditional extinguishing agents, such as water, can conduct electricity and pose a significant safety hazard when used on electrical fires.

The other options mention properties like biodegradability, ineffectiveness against liquids, and the presence of foam additives, which are more applicable to other classes of extinguishing agents or general fire safety protocols. For instance, some agents, like those used in Class B fires, are designed specifically to combat flammable liquids and may indeed contain additives like foam, which is not relevant in the context of Class C extinguishing agents.