What percentage of atmospheric air is formed by nitrogen?

Nitrogen makes up approximately 78% of Earth's atmosphere. This fact is well-established and is crucial for divers to understand because it emphasizes the primary components of the air they breathe during diving. While other gases such as oxygen (about 21%) and trace gases are present, nitrogen's predominant presence is significant in discussions about decompression sickness and gas narcosis.

Understanding that nitrogen constitutes the majority of atmospheric air helps divers recognize how it affects their body during diving activities. For example, at greater depths, increased nitrogen absorption can lead to a higher risk of nitrogen narcosis and decompression illness if the diver ascends too quickly. Familiarizing oneself with these percentages reinforces the importance of safe diving practices and the physiological effects of breathing different gas mixtures underwater.