As your desire to dive deeper and stay longer expands, you leave the realm of recreational diving and the no decompression limits that you were taught. Diving deeper and staying longer at depth moves you into decompression diving. Decompression diving requires detailed planning, preparation, equipment, and mind set and takes you into a very advanced form of diving. If you have the desire to explore wrecks, caves, or whatever that lays in deep water, getting the proper training to safely operate and return from these depths is a must. Before you can return to the surface, you must decompress.
Decompression is stopping at predetermined depths as you ascend to the surface for a predetermined amount of time. The time at each decompression stop depth is determined by how deep you go, what bottom gas you breathed, how long you stayed at depth, what decompression gasses you are using, the physical exertion of the dive, and your personal fitness level.
Decompression is required to remove the inert gasses that you breathed during the dive that was absorbed into your body tissues and organs. The amount of inert gas that is absorbed is based on how deep you go, what bottom gas you breathed, how long you stayed at depth, what decompression gasses you are using, the physical exertion of the dive, and your personal fitness level. Every individual is different and from day to day your body physiology can change, which means that decompression is not an exact science.
Decompression techniques, physiology, theory, procedures, etc. have been studied by many smart scientists, doctors, the U.S. Navy, and mathematicians for many decades. During these years of study many different models, techniques, procedures, etc. where developed, used, and studied to determine how the human body absorbs and off gasses inert gasses. As a result, many different decompression models were developed and decompression tables were developed based on these models.
The tables you receive today in your basic open water training courses are no decompression tables based on a theoretical curve, meaning that the majority of individuals studied didn’t have decompression illness (DCI) symptoms when the tables were followed. Conservative calculations based on this curve are how the no decompression limits were developed. It’s important to note that that doesn’t mean you can’t or won’t get decompression illness if you follow the tables. As mentioned, decompression is not an exact science and each individual is different, therefore individual susceptibility to DCI can vary.
When decompression is required on a dive, there are numerous things on the market that can be used to develop decompression diving tables. Dive computers today are very popular and many provide decompression schedules if needed. Some dive computers allow you to use multiple gasses during your dive and calculate the decompression stop depths and times based on the gasses imputed. Decompression software also is available that runs on standard PCs that can generate very extensive decompression tables. The software programs allow you to enter your dive depth, bottom time, all of the gasses you are using on the dive, safety factors, as well as many other things. Based on the information you input into the software, tables are generated that can then be laminated and carried with you on the dive or copied to a dive slate or wet notes.
Each computer and software application uses algorithms to determine the decompression requirements. There are several different algorithms being used today, which compute decompression requirements based on different criteria. Buhlman, DCIEM, VPM, and RGBM are several of the most popular models being used today. Each has proven effective at various levels and applications.
Decompression study is very active today. Scientists are constantly studying body mechanics and physiology and working with new algorithms. Because decompression is not an exact science, you can bet the research in this area will continue long into the future.