In ARFF, which agent is not routinely used for extinguishing flammable liquid fires?

In the context of Aircraft Rescue and Fire Fighting (ARFF), water is not routinely used for extinguishing flammable liquid fires due to the principle of how it interacts with such substances. Flammable liquids can float on water or may be less dense than water, which can result in the fire spreading rather than being extinguished.

Foam, dry chemical agents, and carbon dioxide are preferred for these types of fires because they effectively suppress the flames and prevent re-ignition. Foam blankets the surface of the burning liquid, cutting off oxygen and cooling the fire. Dry chemicals work by interrupting the chemical reaction of the fire, while carbon dioxide also displaces oxygen around the fire.

Therefore, the correct identification that water is not routinely used aligns well with the best practices in fire suppression for flammable liquids, reinforcing the operational strategies of ARFF personnel when dealing with such hazardous situations.