What is the typical oxygen percentage in standard Air?

The typical oxygen percentage in standard air is 21%. Standard air is composed of approximately 78% nitrogen, 21% oxygen, and trace amounts of other gases, such as carbon dioxide and argon. Understanding the composition of air is crucial for divers, especially when using different gas mixtures, such as nitrox, which have higher percentages of oxygen compared to standard air. This knowledge helps divers manage their oxygen exposure, especially when planning dives and considering potential effects such as oxygen toxicity at deeper depths. Therefore, recognizing that the oxygen content in the air we typically breathe is 21% is foundational for divers in their training and dive planning.