Combustion toxicology is basically concerned with a study of the nature of and potential for adverse health effects with products resulting from the heating and burning of materials. Combustion products are multiple, of a wide range of chemical structures, and are variable in absolute and relative amounts from fire to fire and at different phases in the same fire situation. Depending on the nature of the materials involved in a conflagration, the composition of the smoke produced may result in various acute, short‐term repeated and long‐term adverse consequences. Effects produced include local irritation and tissue injury, incapacitation and systemic toxicity, including lethality. This chapter reviews the incidence and causation of fires, the nature and toxicity of fire atmospheres, factors influencing the generation and effects of combustion products, incapacitating effects, investigation of the toxicological aspects of fires and hazard evaluations. A separate section is devoted to the potential for adverse health effects to fire‐fighters from acute and repeated exposures to fire atmospheres; notably respiratory, cardiovascular, reproductive and carcinogenic hazards.