Any rescue of saturation divers is logistically complicated by the absolute barrier that they must remain at or very near their saturation pressure at all times until they can be decompressed according to a suitable saturation decompression schedule. This means that they must transfer from whatever environment they occupy at the time of the emergency, to a place of safety at effectively the same pressure at all stages. First aid and urgent medical treatment must also be done in the hyperbaric environment. It is not practicable to decompress from saturation outside of a hyperbaric chamber, as the decompression generally takes several days.