Fire is primarily composed of several gases ignited by a source of heat and exposure to oxygen. Visible flames are the result of the energy given off through a chemical reaction caused by the burning of a fuel source.
When a fire burns, it emits large amounts of heat and carbon dioxide from its fuel source through a process of rapid oxidation and combustion. The fire's appearance, heat emission and chemical composition may vary depending on its fuel source and other external materials. The color of the fire may fluctuate with its temperature. Fire may ionize into plasma at extremely high temperatures.