What class of fire involves ordinary combustible materials such as wood and paper?

The classification of fires is based on the types of materials that fuel them, and Class A fires specifically involve ordinary combustible materials such as wood, paper, cloth, rubber, and many plastics. This makes Class A fires the most common type encountered in typical environments, since these materials are widely used in homes, offices, and other structures.

The significance of identifying a Class A fire lies in the appropriate firefighting techniques and agents used to combat it. Water is the most effective extinguishing agent for Class A fires due to its ability to cool the burning materials and reduce their temperature below the ignition point. Understanding this classification is crucial for fire safety measures, planning, and the selection of suitable fire extinguishers in various settings.

Other classes, while related to different materials—such as flammable liquids in Class B, electrical fires in Class C, and combustible metals in Class D—do not include ordinary combustibles, thus differentiating how various types of fires should be handled.