Decompression sickness lessen the pressure reduction, and hence the risk of DCS. All cases of decompression sickness should be treated initially with 100% oxygen until hyperbaric oxygen therapy (100% oxygen delivered in a high-pressure chamber) can be provided. Mild cases of the "bends" and some skin symptoms may disappear during descent from high altitude; however, it is recommended that these cases still be evaluated. Neurological symptoms, pulmonary symptoms, and mottled or marbled skin lesions should be treated with hyperbaric oxygen therapy if seen within 10 to 14 days of development. Recompression on air was shown to be an effective treatment for minor
Scuba set or use lower proportions of oxygen than air. In these situations divers often carry additional scuba sets, called stages, with gas mixtures with higher levels of oxygen that are primarily used to reduce decompression time in staged decompression diving. These gas mixes allow longer dives, better management of the risks of decompression sickness, oxygen toxicity or lack of oxygen (hypoxia), and the severity of nitrogen narcosis. Closed circuit scuba sets (rebreathers) provide a gas mix that is controlled to optimise the mix for the actual depth at the time. Gas cylinders used for scuba diving come in various sizes and