Air

Air is a name for the alloy of gasses present in the Earth's atmosphere.

Dry air is roughly 79% nitrogen, 20% oxygen, and 1% argon. Air may contain 0-7 % water vapour (the 79%, 20% and 1% become accordingly a little less), and less than 1% carbon dioxide. The composition of the air changes with altitude; also exhaled air is different from what is inhaled.

Pressure decreases with altitude; this is why aircraft have pressurised cabins. The air pressure inside aircraft cabins is maintained at a pressure higher than that outside, for the comfort of the passengers and crew, although it is still slightly lower than at ground level. With a decrease in pressure comes a decrease in density, meaning the gases are more spread out at higher altitudes. Because of this, mountain climbers[?] must carry a supply of oxygen on their way up to the summit of high mountains.

Compressed air is often used in scuba diving, when diving fairly close to the surface.

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Air is one of the classical elements, and is associated with many other concepts, such as the sword suit in the tarot.

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Air is a French electronica band. Their acclaimed first album Moon Safari was followed by releases like Premiers Symptomes, 10,000 Hz Legend and the soundtrack to the film The Virgin Suicides.