Which agent is preferred for fighting fires caused by ethanol-based fuels?

The preferred agent for fighting fires caused by ethanol-based fuels is alcohol-resistant AFFF (Aqueous Film Forming Foam). This type of foam is specifically formulated to combat polar solvents like ethanol, which can be more challenging to extinguish than typical hydrocarbon fires.

Alcohol-resistant AFFF works by forming a barrier that separates the fuel from the oxygen, which is critical in extinguishing flames. It is also designed to remain effective even in the presence of alcohol and can tolerate the unique properties of ethanol, such as its ability to mix with water. Regular AFFF might not provide adequate coverage or extinguishing capability because it can break down in the presence of alcohol-based fuels, leading to ineffective firefighting efforts.

In contrast, the other options may not provide the same level of protection or efficiency against ethanol fires. Standard AFFF does not have the necessary resistance to polar solvents, foam concentrate containing water lacks the specific properties to effectively extinguish alcohol-fueled fires, and water mist is not effective by itself in extinguishing fires fueled by alcohols due to potential re-ignition and insufficient cooling capabilities.