Combustible

A combustible substance is a material that can ignite and sustain combustion in air. Combustibles include gases, vapors, liquids, and solids that can undergo exothermic oxidation. The term is used in chemistry, engineering, and fire protection to describe how easily a material can burn and how it behaves in a fire.

In fire safety, liquids are often classified by flash point. Flammable liquids have a flash point below 37.8 °C (100 °F); combustible liquids have a flash point of 37.8 °C or higher. Gases may be described as flammable when their mixtures with air can ignite at ambient conditions. Solids can be combustible as well, depending on how readily they release heat when heated. Important related properties include the flash point, autoignition temperature, and heat of combustion.

Examples include flammable liquids such as gasoline and acetone; combustible liquids such as diesel; flammable gases such as propane; and combustible solids such as wood and paper. The practical implications of combustibility drive storage, labeling, ventilation, and ignition-source control to reduce the risk of fires and explosions.