Complex sentence: Nitrox refers to any gas mixture composed (excluding trace gases) of nitrogen and oxygen; this includes normal air which is approximately 78% nitrogen, 21% oxygen, and 1% other gases, primarily argon.
Split into simpler sentences: Nitrox refers to any gas mixture composed (exccepting trace gases) of nitrogen and oxygen. This includes atmospheric air, which is approximately 78% nitrogen, 21% oxygen, and 1% other gases, primarily argon.