Combustion Combustion is the process by which something burns. Combustion is a chemical reaction between a carbon-containing fuel and oxygen in the atmosphere. To start and continue, the reaction requires heat. The fire triangle illustrates the three key components that keep a fire burning. A fire only keeps burning if it has enough fuel, oxygen, and heat.
Fuel is any substance that can burn.
For example, gasoline, paper, candle wax, and trees all burn. Therefore they are all fuels. When a fuel burns it releases chemical energy. This energy can be seen in the form of light and felt in the form of heat. The hot light that results from the process of combustion is called a flame.