Dive computer decompression models and algorithms: philosophical and practical views

The functioning of diving decompression computers is based on predictive models that are made operational through algorithms. Relatively simple models can be constructed to manage diving decompression obligations with a high degree of confidence, as long as the dive profiles fall within the model’s ‘range of applicability’. The same degree of confidence cannot be assumed where dive profiles are outside of that range – for instance by diving deeper, or for longer or more frequently than what had been considered in the development of the model, or because of individual physiological particularities. A common method to deal with this is to increase the level of conservatism of the model by reducing inert gas load. Depending on the dive computer, this is achieved by allowing the diver to set predefined ‘personal levels’ or through ‘gradient factors’, which is a more transparent method of obtaining a reduced inert gas load at the end of a dive. This paper outlines models and algorithms in general, and then discusses gradient factors in further