Common signs and symptoms of diving disorders can be observed either during a dive, on surfacing, or up to several hours after. Diving disorders are caused by breathing gas at the high pressures encountered at depth: when diving, the gas breathed must be at the same pressure as the ambient pressure, which can be much greater than on the surface, increasing by one standard atmosphere (100 kPa) for every 10 metres (33 ft) of depth. The principal conditions encountered are decompression illness (which covers decompression sickness and arterial gas embolism); nitrogen narcosis; high-pressure nervous syndrome; oxygen toxicity; and pulmonary barotrauma (burst lung). Although some of these may occur in other settings, they are of particular concern for divers. (Full list...)