Combustion reactions involve the interaction between a fuel and an oxidant. The result of this type of reaction is heat and/or light. It may occur either in a fast pace, or in a slow manner. Types of Combustion Reactions Rapid Combustion: A very basic example of this type is fire. In this reaction, heat and light are produced in high amounts. In some cases, a large amount of gas is also produced, and this gives rise to a buildup of excessive pressure, which could be manifested by a loud noise, known as an explosion. Slow Combustion: In this reaction, the temperature at which the combustion operates is very low, and hence, the process is devoid of flames. It is also known as smoldering combustion, which only occurs on the surface. The rate at which this combustion proceeds is ten times slower than that of rapid combustion. Cellular respiration: The body obtains energy as a result of this reaction. This energy is produced along with carbon dioxide and water, when glucose (that acts as the fuel) reacts with oxygen (as the oxidant). Due to the relatively slow nature of combustion, the heat generated in this process is not manifested as the fire that occurs when wood is burnt. Combustion of fossil fuels: Burning up of hydrocarbons (organic compounds containing only carbon and hydrogen) is a common example of combustion reactions. Methane, CH⁴, propane, C³H⁸, butane, C⁴H¹⁰, and octane, C8H¹⁸, are some of the hydrocarbons that can undergo combustion. The two kinds of combustion that may take place in this case are: complete and incomplete. In the former type, the reaction takes place with ample oxygen, yielding a limited number of products, such as energy, carbon dioxide, and water vapor. For example, when methane burns in oxygen, it yields carbon dioxide and water. The reaction: CH₄ + 2O₂ → CO₂ + 2H₂O In the latter type of reaction, oxygen is not present in a quantity that is required to produce carbon dioxide and water. This means that the fuel is not allowed to react completely with oxygen. In other words, the reaction remains incomplete, as a result of which, it yields products that would be created in a complete combustion process, along with few other products. An example of this may be the reaction of methane in presence of an inefficiency of oxygen. This reaction might produce carbon monoxide and water. When the oxygen is decreased further, it may also form carbon and water. The reactions: CH₄ + 1.5O₂ → CO + 2H₂O CH₄ + O₂ → C + 2H₂O Thus, the above chemical reaction examples provide some glimpses into the phenomenon of combustion. These reactions are very important for existence of life processes on our planet.