Does the Percentage of Oxygen In The Air Change With Altitude?
No, the radio of oxygen to nitrogen in the composition of the air does not change. The 21% of oxygen in the air remains relatively constant at altitudes up to one 100,000 feet. Why Must We Use Extra Oxygen When We Ascend In Altitude? The blanket of air which surrounds our planet is several hundred miles thick, compressible, and has weight. The air closest to the earth is supporting the weight of the air above it and, therefore is more dense; its molecules are packed closer together. As we ascend in altitude the air is less dense. For example, at 10,000 feet, the atmospheric pressure is only 2/3 of that at ground level. Consequently, the air is less dense, and each lungful of air contains only 2/3 as many molecules of oxygen as it did at ground level. At 18,000 feet the atmospheric pressure is only 1/2 of that at ground level. Although the percentage of oxygen is still the same as at ground level, the number of molecules of oxygen in each lungful is reduced by 1/2. As we ascend, there i
