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Three Requirements for Combustion Reactions

Of all chemical reactions, combustion is probably the one most familiar from everyday life. Combining a lit match, air and a fireplace log is sufficient to start the combustion reaction called fire. The lit match, the fuel and the air are just specific examples of the three general conditions required for any combustion reaction.

Oxidizing Agent
- All combustion reactions require the presence of a type of compound called an oxidizing agent. Oxygen is a common oxidizing agent, although there are many others. Chemists have found it possible to burn sand with a gas called chlorine trifluoride, for example, and oxidizing agents like perchloric or chloric acid react explosively with organic compounds like paper and sugar. Nonetheless, oxygen is the most abundant and readily available oxidizing agent, so typical combustion reactions like the one in your fireplace involve oxygen.
Fuel
- All combustion reactions require a fuel, a material that reacts with the oxidizing agent to release energy in the form of heat. Organic compounds like those found in wood, gasoline and sugar are the most common fuels. A compound may serve as a fuel in some combustion reactions but not in others. Oxygen, for example, cannot burn sand but chlorine trifluoride can do so. Since oxygen is the agent you encounter in everyday life, however, the key criterion is whether the fuel reacts with oxygen.
Ignition Source
- The third requirement for combustion reactions is an ignition source to give the reaction a push and get it started. Heat and sparks can both ignite fuels. If you have both a fuel and an oxidizing agent present in the same place, sparks are always dangerous and should be avoided. If you're dealing with a liquid fuel, one of the most important considerations is the flash point, the temperature at which the vapor may ignite.
Considerations
- Combustion reactions can be very useful. Power plants and automobiles, for example, derive energy from burning fuels like coal and liquid hydrocarbons. Despite their usefulness, however, combustion reactions can also be very dangerous. According to the U.S. Fire Administration, accidents with fire claimed 2,480 lives in the U.S. in the year 2009 alone. To prevent fires and other combustion reactions from occurring, you want to make sure the three ingredients for combustion do not come into contact with each other. If you have a fuel like wood or gasoline, for example, you should make sure it stays away from possible ignition sources ̵2; and vice versa.

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