Fires are classified based on what criterion?

Fires are classified based on what is burning because this criterion directly affects the combustion process and determines the appropriate firefighting methods and materials needed to control or extinguish the fire. Different materials and substances burn in distinct ways, producing varying flames, smoke characteristics, and levels of toxicity, which influence the strategies and equipment that firefighters must use.

For instance, fires involving ordinary combustibles such as wood and paper are categorized as Class A fires. In contrast, fires involving flammable liquids like gasoline are classified as Class B fires. Understanding what fuels the fire is critical for effective hazard assessment and response planning, as it informs the selection of extinguishing agents. These principles are essential knowledge within the context of firefighting and align closely with the guidelines set forth in NFPA 1081 and other related standards.