Air is approximately composed of what percentage of Oxygen?

Air is composed of approximately 21% oxygen by volume. This percentage is significant because it highlights the role of oxygen in sustaining life, as it is essential for the respiration of most organisms. The composition of air is relatively stable, with nitrogen making up about 78%, carbon dioxide and other gases making up the remaining percentage. Understanding the composition of air is crucial for various applications, including combustion processes in heating systems, where an adequate supply of oxygen is necessary for efficient fuel burning. This knowledge helps professionals manage air quality and system efficiency in heating and boiler setups.