Which dry chemical agent is suitable for Class A protection?

The use of ammonium phosphate-based agents as a dry chemical for Class A protection is appropriate because these agents are designed to combat fires involving ordinary combustibles, such as wood, paper, and fabric. Ammonium phosphate acts not only by smothering the fire but also by creating a cooling effect when expelled, which helps to prevent re-ignition of the materials involved. This dual-action makes it particularly effective for Class A materials.

In comparisons to other agents, potassium bicarbonate and sodium bicarbonate are primarily effective against flammable liquid fires (Class B), making them less suitable for Class A fires. Corrosive agents, on the other hand, are not utilized as extinguishing agents and can cause additional hazards. Thus, ammonium phosphate stands out as the most suitable choice for Class A fire protection among the options provided.