What is the most common extinguishing agent for Class A fires?

Water is recognized as the most common extinguishing agent for Class A fires, which involve ordinary combustibles such as wood, paper, cloth, and some plastics. Water is effective in cooling the burning material and reducing the temperature below the ignition point, which is essential to extinguishing the fire. It also serves to create steam, which can help smother the fire by displacing oxygen in the area.

Using water is advantageous because it is readily available, inexpensive, and non-toxic, making it a widely preferred choice in firefighting scenarios involving Class A fires. Its ability to absorb heat and lower the temperature of burning materials is a crucial factor in effectively extinguishing these types of fires.

The other extinguishing agents listed have specific uses or limitations: CO2 is effective primarily for Class B and C fires and is less effective for extinguishing Class A fires because it does not cool materials; dry chemical agents are versatile but generally used for a wider range of fire types; and carbon tetrachloride is not commonly used due to health risks and environmental concerns.