Combustion is a fast chemical reaction between combustible component(s) and an oxidizing agent. Mostly air is used for combustion. Dry air contains and  and so 1 mole of  carries with it 3.76 moles of N₂. Combustion equations with air, when complete combustion takes place are

	(1)
	(2)
	(3)
	(4)

Similarly, for other hydrocarbons combustion reactions can be written. Note that complete combustion refers to conversion of  or  into  and