Nitrox refers to any gas mixture composed (trace gases excluded) of nitrogen and oxygen, this includes normal air which is approximately 78% nitrogen and 21% oxygen, with around 1% other gases. The most common use of nitrox mixtures containing higher than normal levels of oxygen is in SCUBA diving where the reduced percentage of nitrogen is advantageous in reducing nitrogen take up in the body's tissues and so expend the possible dive time and/or reducing the risk of decompression deseases (well known as the bends).