Combustion or burning is an exothermic reaction between a substance and a gas to release heat. Combustion normally occurs in oxygen (often in the form of gaseous O2 ) to form oxides, However, combustion can also take place in other gases like chlorine. The products of such reactions usually include water (H2 O) as well as carbon monoxide (CO) or carbon dioxide (CO2 ), or both. Other by-products, such as partially reacted fuel and elemental carbon (C), may generate visible smoke and soot. This book presents leading research from around the world in this frontal field.