As a respiratory specialist, I can tell you that the amount of oxygen a person needs can vary greatly depending on factors such as activity level, health, and environmental conditions. However, on average, a person at rest consumes approximately 550 liters of oxygen per day. This figure is derived from the fact that each breath we take consumes about 5-percent of the air inhaled, which is then converted into carbon dioxide. It's important to note that this is a rough estimate and the actual amount can fluctuate. For instance, someone who is exercising will use significantly more oxygen to meet the increased demands of their body. read more >>

Therefore, about 5-percent of breathed air is consumed in each breath. That air is converted to carbon dioxide. So, as far as how much air is actually used, human beings take in about 550 liters of pure oxygen per day. A person who is exercising uses a lot more oxygen than that.read more >>