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Yes and no.

Yes, air composition is basically the same everywhere on the surface of the Earth: it's approximately 79% nitrogen, 20% oxygen, 1% a mix of lots of other stuff. Those percentages can vary slightly, and that 1% can include LOTS of things. Air composition can also vary due to pollutants. Some places have more pollutants in the air than others, and these pollutants can be different, too. 

Air pressure is different depending on your altitude. At sea level, air pushes at 1 kilogram per sqare centimeter (14.7 pounds per square inch), but at the top of Mt. Everest, air is less dense and exerts a pressure of 0.3 kilograms per square centimeter (4.5 pounds per square inch).