Decompression When a diver ventures underwater the pressure on their body increases. The deeper you go the more the pressure increases. As a result the air, or other gas, that is breathed also increases in pressure. The body`s tissue absorb inert gasses until the pressure between the gas breathed in and the dissolved gas are in balance. In everyday life our bodies are saturated with nitrogen, the main inert gas in the atmosphere. Underwater the body gradually begins to absorb more inert gas, again normally nitrogen since most divers breathe nitrogen based mixtures and most often compressed air. When the diver returns to the surface this nitrogen begins to exit the body`s tissues. This process can cause bubbles and these in turn can damage the body. This is known as decompression illness (DCI). In order to prevent DCI divers must limit their time underwater or stop during the return to the surface in order to let some of the dissolved gas escape. These stops are called decompression stops. This process was understood many years ago when the Navy commissioned a man called John Scott Haldane to investigate DCI. Haldane researched the problem and calculated a set of tables that gave the divers and caisson workers of the day the information they needed in terms of how long and how deep one could go and what decompression stops were needed on the return to the surface. Although Haldane died in 1936 many other people have carried on the research into DCI. The best known of these is probably Albert A. Bühlmann a Swiss doctor whose name is generally associated with most modern decompression theory. Modern decompression theory is a far more complicated thing than the original Haldane understanding. Bubble physics and other breathing gasses have refined the models and modern computer technology has made complex calculation easy. As a result most divers now have a personal dive computer that tracks the depth and time and displays the decompression information the diver needs to make a safe return to the surface.