Abstract
The safe transition from a higher pressure atmosphere to a lower pressure atmosphere is accomplished by planning the decompression process, typically through changes in pressure and/or composition of the breathing mix in a function of time. However, the decompression process is affected by a much greater number of inherent factors than changes in pressure and composition of the breathing mix. Their values should be kept within certain ranges, however, there are circumstances when it is not possible to maintain control over them. In this situation, they become elements of the residual risk of the decompression process. The safety of decompression should be ensured, inter alia, by analysing the residual risk for each execution of the decompression process.