What is the main factor determining the classification of a fire?

The primary factor determining the classification of a fire is the type of fuel involved. Fires are categorized into different classes based on the materials that are burning, as different fuels react differently to extinguishing methods. For example, Class A fires involve ordinary combustibles such as wood, paper, and cloth; Class B fires involve flammable liquids and gases, like gasoline; Class C fires are electrical fires; Class D involves combustible metals; and Class K pertains to cooking oils and fats. Understanding the type of fuel is crucial because it influences the appropriate methods of suppression, safety measures, and handling procedures necessary for effective fire response. Recognizing this classification helps in efficiently managing fire hazards during firefighting and rescue operations.