Water-based extinguishers are fire safety devices that use water to extinguish flames. They are most effective on Class A fires, which involve ordinary combustibles like wood, paper, and cloth. These extinguishers work by cooling the burning material and reducing the heat to a point where combustion can no longer occur. These extinguishers are typically easy to use and are identified by a red label. However, they should not be used on Class B fires (flammable liquids) or Class C fires (electrical equipment), as water can spread the fire or create electrical hazards. Always check the label for proper usage.