What type of fire primarily uses water as an extinguishing agent?

The type of fire that primarily uses water as an extinguishing agent is Class A. Class A fires involve ordinary combustible materials, such as wood, paper, cloth, and most plastics. Water is effective in extinguishing these fires because it cools the burning material and reduces the temperature below the ignition point. Additionally, water helps to smother the fire by soaking the combustible materials, which prevents further combustion.

In contrast, other classes of fires, such as Class B (flammable liquids and gases), Class C (electrical equipment), and Class K (cooking oils and fats), require different extinguishing agents due to the nature of the materials involved. Using water on Class B and Class C fires can be dangerous, as it can spread the fire or create electrical hazards. Class K fires, typically found in kitchens, require specialized extinguishing agents that can effectively manage the unique risks associated with cooking oils.