sentences:  These rates are lower than those previously reported for military personnel, recreational divers in the UK, recreational divers in the Caribbean, recreational divers in western Canada and wreck divers in cold water.Nitrox has been used for open circuit scientific diving since the early 1970s with no evidence of increased DCS risk in comparison with similar air dives.A maximum oxygen partial pressure of 1.6 bar has been found generally acceptable for open circuit nitrox diving by the scientific community, and it has not been found necessary to screen for carbon dioxide retention.