NEBULA

combustion: burning of a substance in the presence of oxygen to heat and light  or  burning , [1]  is a high-temperature  exothermic   redox   chemical reaction  between a  fuel  (the reductant) and an  oxidant , usually atmospheric  oxygen , that produces oxidized, often gaseous products, in a mixture termed as  smoke . Combustion in a  fire  produces a  flame , and the  heat produced can make combustion self-sustaining. Combustion is often a complicated sequence of  elementary   radical reactions .  Solid fuels , such as  wood  and  coal , first undergo  endothermic   pyrolysis  to produce gaseous fuels whose combustion then supplies the heat required to produce more of them. Combustion is often hot enough that  incandescent   light  in the form of either  glowing  or a  flame  is produced. A simple example can be seen in ...