In the extraction process of steel, one of the step is purification of the iron used to make the steel. In which pure oxygen is blown on the steel at high temperature so that the carbon percentage present in the steel can be thrown out in the form of gas. The process occurs at high temperature which is called combustion process. The reaction occurs can be shown as- C(s)+→C (g) + CO (g). In presence of excess oxygen, the produced carbon mono oxide (CO) converts to carbon di-oxide. The reaction is CO(g) + (g) → C (g). From the density of the evolved gas one could identify the gas. If the gas density is 1.77g/L which is very close to the standard density of C i.e. 1.80g/L, the gas is carbon dioxide only.