As a respiratory physiologist, I can tell you that the amount of oxygen an individual needs can vary greatly depending on several factors, including age, health, activity level, and environmental conditions. On average, a person at rest consumes about 550 liters (19.4 cubic feet) of air per day, which contains approximately 20.8% oxygen. This translates to about 24 grams of oxygen daily. However, during periods of increased physical activity, the body's demand for oxygen can rise significantly.

During exercise, the body may require up to 10 to 20 times more oxygen than at rest. For example, a person engaging in heavy exercise might need up to 35 liters (1.25 cubic feet) of oxygen per minute. It's important to note that the human body has mechanisms to increase oxygen intake and delivery to tissues during periods of increased demand, such as increasing the breathing rate and depth, and enhancing the efficiency of oxygen utilization by the muscles.

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The average adult, when resting, inhales and exhales about 7 or 8 liters of air per minute. That totals about 11,000 liters of air per day. Inhaled air is about 20-percent oxygen. Exhaled air is about 15-percent oxygen.read more >>