Which extinguishing agent is typically inappropriate for Class B fires?

Water is typically inappropriate for Class B fires because these types of fires involve flammable liquids, such as gasoline, oil, or solvents. Using water as an extinguishing agent can be dangerous because it may cause the flammable liquid to spread, leading to a larger fire and increased risk of injury or damage. Water can also vaporize the flammable liquid, creating explosive vapors.

In contrast, agents like AFFF foam, dry powder, and carbon dioxide are specifically designed to handle flammable liquids. AFFF foam smothers the fire while also providing a barrier to prevent re-ignition. Dry powder extinguishers work by breaking the chemical reaction of the fire, while carbon dioxide displaces oxygen, effectively suffocating the fire. These agents are appropriate for Class B fires, making water the unsuitable choice in this context.