For complete combustion, what are the percentages of oxygen and nitrogen in the air required?

Complete combustion occurs when a fuel reacts with oxygen in the air to produce carbon dioxide, water, and heat, without any unburned fuel or hazardous by-products. The composition of air is a critical factor for achieving complete combustion.

Air is primarily composed of approximately 21% oxygen and 79% nitrogen by volume. For complete combustion to take place efficiently, an adequate supply of oxygen is essential to fully oxidize the fuel. The correct answer reflects the typical composition of air in a natural environment, making it vital for combustion processes in fireplaces and stoves.

The choice indicating 20% oxygen and 80% nitrogen accurately represents the standard conditions of ambient air, which aligns with the requirements for complete combustion. This ensures that the combustion process can proceed smoothly, minimizing the production of unwanted emissions and maximizing energy efficiency.