What is the primary component of the air we breathe?

The primary component of the air we breathe is nitrogen, which makes up about 78% of the Earth's atmosphere. This fact highlights its dominance compared to other gases present in the air. While oxygen is vital for respiration and comprises approximately 21% of the atmosphere, it is not the most abundant gas. Carbon dioxide and argon are present in even smaller amounts, with carbon dioxide making up about 0.04% and argon about 0.93% of the atmosphere. Understanding this composition is essential, especially in HVAC applications, as it influences the calculations and considerations for air quality, ventilation, and system design.