What is the primary method for extinguishing a Class A fire?

The primary method for extinguishing a Class A fire is water or foam because these types of fires involve ordinary combustible materials such as wood, paper, and cloth. Water effectively cools the fire and reduces the heat to below the material's ignition temperature, thereby suppressing the flames. Foam can also be used as it not only cools but also forms a barrier that can help prevent re-ignition by smothering the fire.

In contrast, dry powder extinguishers and CO2 extinguishers are typically more effective for other classes of fires, such as flammable liquids or electrical fires, where cooling and smothering are accomplished differently. Sand or dirt might be used in certain contexts but is not the most effective primary choice for extinguishing Class A fires, as it does not provide the necessary cooling effect as water does.