What might happen if water is used on a Class B fire?

Using water on a Class B fire, which typically involves flammable liquids such as gasoline, oils, or paints, can cause the fire to spread further. This happens because water does not extinguish the flammable liquid itself; rather, it can cause the liquid to float on the surface of the water and spread out, thereby increasing the area of the fire. Additionally, water may vaporize the flammable material, creating a hazardous vapor that can ignite and cause the flames to spread.

Therefore, using water on Class B fires is not only ineffective but potentially dangerous, emphasizing the importance of using appropriate extinguishing agents, such as foam or dry chemical extinguishers that are specifically designed for these types of fires.