For which class of fire is the H2O fire extinguisher suitable?

The H2O fire extinguisher is specifically designed for Class A fires, which involve ordinary combustible materials such as wood, paper, cloth, and some types of plastics. The extinguishing agent in an H2O extinguisher is water, which cools down the burning material below its ignition temperature, thus effectively extinguishing the fire.

Using water on Class A materials is effective because it removes heat, which is one of the essential elements of the fire triangle (heat, fuel, and oxygen). However, it's important to note that water is not suitable for extinguishing fires involving flammable liquids, electrical equipment, or reactive metals, which are Class B, C, and D fires respectively. For those types of fires, other extinguishing agents are recommended to prevent dangerous reactions or further fire spread.