The most significant source of losses during combustion is exhaust stack especially when airflow is not monitored during combustion. When fuel is burned in the presence of oxygen, the products of combustion are obtained as heat, water and carbon dioxide. The amount of oxygen required for combustion depends on the composition of the fuel. Highest efficiency is obtained when complete combustion occurs while minimizing excess air hence preventing energy loss through the exhaust stack. A balance between the amount of fuel and air required during combustion is defined by air to fuel ratio (AFR) (Kolev, Nikolay Ivanov 128). Optimum AFR is desired in ensuring highest efficiency. Graph of carbon dioxide against air-fuel ratio shows a decrease in the amount of CO2 produced when the AFR increases. On the other hand, an increase in oxygen leads to a decrease in AFR. When AFR increases, more combustion occurs allowing for complete combustion of the fuel. Therefore, more energy is produced, and less carbon dioxide is produced. An increase in the amount of oxygen increases the air-fuel ratio allowing for complete combustion. An increase in air-fuel ratio increases the efficiency of the system and also reduces the exhaust stack in the system. From the data provided and the graphs, it is evident that combustion efficiency is influenced by the amount of oxygen provided in the system.The air-fuel ratio defines the efficiency by determining whether combustion is complete or not. Energy produced is higher for a high-efficiency system compared to a low-efficiency system. Airflow rate influences the amount of energy produced in the system. Percentage of flue heat increases with a decrease in the amount of oxygen provided in the system (Kolev, Nikolay Ivanov 267). Heat taken by water from the system increases as the flow rate decreases, gas flow rate influences the combustion rate hence affecting the amount gained by water and overall efficiency of the system. Work Cited Kolev, Nikolay Ivanov. Multiphase Flow Dynamics. [Berlin], Springer, 2014,.