What type of gas constitutes the majority of normal air?

The majority of normal air consists of nitrogen, which makes up about 78% of the Earth’s atmosphere. This high concentration of nitrogen plays a crucial role in various atmospheric and biological processes. Unlike oxygen, which is essential for respiration and combustion, nitrogen is largely inert and does not actively participate in chemical reactions under normal conditions. Its predominance in the atmosphere is vital as it acts as a buffer and diluent for oxygen, preventing excessive combustion and aiding in maintaining stable atmospheric pressure for aquatic and terrestrial life.

While oxygen is critical for life, constituting about 21% of the atmosphere, nitrogen’s abundance is what defines the composition of normal air more significantly. Other gases like hydrogen and carbon dioxide are present in much smaller quantities, with carbon dioxide being around 0.04% of the atmosphere. Understanding the composition of air is essential for divers, as breathing gas mixtures that deviate too much from these proportions can pose serious health risks, including narcosis or toxicity. Hence, recognizing that nitrogen makes up the bulk of normal air is fundamental to comprehending the dynamics of diving practices and safety.