That's unfortunately a rather ambiguous term because, of course, we do decompress as weĪscend to the surface again. No-decompression diving?Īs stated above, recreational dive planners are for "no-decompression" diving. In fact, if anything, be even more conservative when planning your dives than the table data suggests. Do not take that to mean you should simply use the numbers as loose guidelines. You might guess that the recreational dive tables have a significant safety margin built in. In 1988, Diving Science & Technology introduced the first dive tables for no-decompression recreational diving.
The data is the result of applying the gas laws on the human body, by making certain guesses, developing certain models, and by numerous studies, observations andĪll of that led to the "dive tables" that were first used by the Navy, and then, as recreational scuba diving became popular, modified for recreational use. The tables have been around for about a hundred years and are all based on data originally developed by the United States Navy. They simply tell you how many minutes you can stay, max, at certain depths without having to do decompression stops, something that is not part of recreational diving and that you should never have to do as a recreational diver. Recreational dive planners do not actually tell you how much nitrogen is inside your body. They tell you how long you can dive at certain depths and how long it will take to get rid of all the extra nitrogen in your system. This is why it is essential to slowly and safely release nitrogen as you ascend, and not build up too much in the first place. Rapidly bubbling out of your tissues and clogging up your blood circulation orīubbles getting lodged in other areas. Much more slowly and much less dramatically, of course. This same thing is happening in your body as you ascend. Shake either a bit and you really see how gases get expelled from a liquid as pressure suddenly drops. It's even more dramatic when you pop open a can of beer. That happens because the pressure inside the bottle dropped when you unscrewed the cap. When you unscrew the cap, pressure is suddenly reduced and the soda foams as carbonation is released. As we come back up, the pressure decreases, the fluids in our body can carry less absorbed gas, and the nitrogen gets expelled from the tissues again.įor a simple, somewhat dramatic, visual explanation of how absorbed gas leaves a liquid as pressure decreases, picture a bottle of carbonated soda that's been shaken a bit. When diving, and ever more so the deeper we dive. Since the pressure under water is considerably higher than above water, our body absorbs more nitrogen In those sections you learned that according to William Henry's law, the amount of gas a liquid can absorb My suggestion is to use and understand one set of tables and stick with them.Īs explained in the "Physics" and "Physiology" sections, when we dive, our body tissues absorb nitrogen. It's like driving a car where the gas is on the left and the brake on the right, and one calls the gas "accelerator" and the other "velocity increasing accentuator". So the NAUI tables are a bit different from the PADI tables, and they use different definitions and acronyms - just enough to throw you off. What's especially frustrating is that all dive tables do essentially the same thing, just not exactly the same way (and often with surprisingly different results).
(see the NAUI table above, and click on it to see a larger copy), but you're still dealing with well over 400 numbers. NAUI uses different dive tables, with all tables being on the same side Student must understand before s/he successfully completes the PADI Open Water Scuba Diver course and gets the certification card contains over a thousand numbers on both sides of a small 5 x 7 inch plastic card. It seems inconceivable that they'd ever understand them, let alone become proficient in using them.Īnd truth be told, dive tables - called "Recreational Dive Planners" by PADI and just "Dive Tables" by NAUI - do look complicated and intimidating with their tables and charts and unfamiliar terminology.Įven the supposedly friendly PADI recreational dive planner that every To many aspiring scuba divers, Dive Tables are scary. In this section we explain dive tables and go through specific examples of repetitive dives, using both the PADI and the NAUI tables.ĭive tables are used to determine how long you can safely stay under waterĪt a given depth, both for the initial dive and for subsequent dives.
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