The chemistry of combustion is well researched and generally accepted. Efficient combustion of natural gas requires combining fuel gas and air in precise ratios. Stoichiometric combustion (a chemistry-based equation) occurs when fuel and air are perfectly balanced. Maximum thermal efficiency occurs with a small amount of excess air.
The natural gas combustion profile (Fig. 1) shows the interaction of certain constituents of interest occurring in a typical burner exhaust stream when firing at a unique, fixed rate under a given set of environmental conditions. The profile illustrates the relationships between exhaust stream oxygen (O2), unburned fuel (hydrocarbons), carbon monoxide (CO), carbon dioxide (CO2) and burner efficiency.