Does altitude change the percentage of oxygen in the air?

The percentage of oxygen is the same at sea level as it is at high altitudes, which is roughly 21 percent. However, because air molecules at high altitudes are more dispersed, each breath delivers less oxygen to the body. A breath at 12,000 feet (3,657.6 m), delivers 40 percent less oxygen to the body than it does at sea level. At 18,000, feet, a breath takes in 50 percent less oxygen. As a result of this difference, you should expect to feel short of breath during and shortly after physical activities, such as mountain climbing or biking,at higher altitudes.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.