What is the approximate percentage of oxygen in air?

The approximate percentage of oxygen in air is about 21%. This percentage is widely recognized in scientific literature and is essential for understanding how the respiratory system operates. Oxygen is one of the primary components of air, which includes nitrogen, argon, carbon dioxide, and other trace gases. The ratio of 21% oxygen is crucial for sustaining life and plays a significant role in various biological processes, such as cellular respiration. Knowing this standard figure helps EMTs and other medical personnel assess situations involving breathability, oxygen supply, and to make informed decisions during emergencies or medical scenarios.