On which type of fires would a wetting agent primarily be used?

A wetting agent is primarily used on Class A fires, which involve ordinary combustibles such as wood, paper, and cloth. These types of fires can be particularly stubborn, especially when they occur in deep-seated bulk materials like piles of leaves or lumber. The use of a wetting agent helps to reduce the surface tension of water, allowing it to penetrate better into the materials being extinguished. This penetration is crucial for effectively cooling the materials and preventing rekindling, as the water can access deeper layers that might not be reached with traditional firefighting methods.

In contrast, while other classes of fires may require different extinguishing agents, a wetting agent is not suitable for Class B fires (flammable liquids), Class C fires (electrical equipment), or Class D fires (combustible metals). Each of these classifications has specific extinguishing needs due to their unique properties and dangers. Therefore, using a wetting agent is most effective and particularly relevant in managing and extinguishing Class A fires involving deep seated bulk material.