IANTD DIVE TABLES PDF

The program qualifies divers to perform no stop dives using Recreational Trimix Gas mixtures within the limits of the existing qualification level to a maximum depth limit of 39 msw fsw. An essential component of this program is equipment configuration which is covered in a series of lectures and practical workshops. The aim being to construct a safe self sufficient equipment configuration that is streamlined, accessible and promotes familiarity. Theory covered includes the END concept, oxygen physiology, oxygen tracking, the use of EANx as a decompression gas, gas switching techniques, partial pressures and best mixes. This program qualifies divers to dive to 45 msw fsw and to perform unlimited decompression utilising EANx decompression mixtures with an oxygen concentration no greater than 1.

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Dive tables are used to determine how long you can safely stay under water at a given depth, both for the initial dive and for subsequent dives. To many aspiring scuba divers, Dive Tables are scary. And there are other formats as well. My suggestion is to use and understand one set of tables and stick with them.

So what does a dive planner do? As explained in the "Physics" and "Physiology" sections, when we dive, our body tissues absorb nitrogen.

Since the pressure under water is considerably higher than above water, our body absorbs more nitrogen when diving, and ever more so the deeper we dive. 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. When you unscrew the cap, pressure is suddenly reduced and the soda foams as carbonation is released.

That happens because the pressure inside the bottle dropped when you unscrewed the cap. Shake either a bit and you really see how gases get expelled from a liquid as pressure suddenly drops. This same thing is happening in your body as you ascend. Much more slowly and much less dramatically, of course. You do NOT want nitrogen rapidly bubbling out of your tissues and clogging up your blood circulation or bubbles getting lodged in other areas.

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. That is where the dive planners come in. 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.

Recreational dive planners do not actually tell you how much nitrogen is inside your body. 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. The tables have been around for about a hundred years and are all based on data originally developed by the United States Navy. 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 and tests conducted over many years.

All 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. You might guess that the recreational dive tables have a significant safety margin built in. Do not take that to mean you should simply use the numbers as loose guidelines. No way. In fact, if anything, be even more conservative when planning your dives than the table data suggests. No-decompression diving? As stated above, recreational dive planners are for "no-decompression" diving.

What it really means is that the data in the tables shows the length of time you can stay at a certain depth and still be able to ascend without making mandatory scheduled "decompression stops. And a minute at half your maximum depth.

How to use the dive tables Now what do Dive Tables do? They tell you how long you can stay, maximum, at certain depths and then come straight back up, without any decompression stops. You do that dive, enjoy the scenery, and then come back up.

Can you now just use that same dive table, strap on a fresh tank of air, and go right back down for a second look at that reef? Residual nitrogen after a dive See, the problem is that while science has determined that it is safe to ascend from 60 feet after 35 minutes -- "safe" meaning that nitrogen gets released at a sufficiently slow rate so as not to pose a danger -- it does NOT mean ALL the nitrogen that was absorbed into your body down there was released during ascent.

Some of the fizz stays in, and only after a few hours or even a day or two does it go all "flat. What that means is that if you dive again, you still have some extra nitrogen in your body, and therefore reach the maximum safe time limit of nitrogen absorption sooner.

It essentially tells you how much nitrogen leaves your body over the time you spend on the surface, sitting on the deck of the dive boat. That is where the "Letter Groups" come in. After your first dive you are in a certain Letter Group, as shown in Table 1. That 35 minute dive to 60 feet put you in Letter Group G you always round up. Table 2 shows what Letter Group you will be in after a certain "surface interval," i. Obviously, the longer you wait, the more of the extra nitrogen your body absorbed during the first dive gets released.

So what the Dive Tables do is determine how much extra nitrogen is still in your body after a dive, and then convert that into "Residual Nitrogen Time," or "RNT. As is, "Residual Nitrogen Time" tells you how much time at a certain depth it would take to absorb the amount of nitrogen you already have in your body from the previous dive, and you can find that in Table 3, the Repetitive Dive Timetable. What does that mean? Well, if the table says your residual nitrogen time is 20 minutes for a given depth, then you can stay at that depth 20 minutes less than on your first dive because, after all, you already absorbed that much nitrogen and it still is in your system.

We follow "G" down into Table 2 and then find the new Letter Group for a 30 minute surface interval. That would also be Letter Group "G". Then we look at the cell where row G intersects with the 50 feet column in Table 3. There will be two numbers: 56 on top number in blue and 24 on the bottom bold number in red.

The top number is your residual nitrogen time RNT. The second number, 24, is your adjusted maximum dive time AMDT , the time you cannot exceed on the dive. In other words, your actual bottom time can be no more than that.

So where do you stand after your second dive? So your total bottom time is now 76 minutes. Now go back to Table 1 and see what Letter Group 76 minutes at 50 feet puts you in. As stated above, although you only stayed for 20 minutes at 50 feet on the second dive, you need to add the 56 minutes of residual nitrogen you still had in your system, i.

If you now plan on waiting an hour and 15 minutes, and then go see that reef at 50 feet again, you find yourself in the new Letter Group H. Now move left to Table 3. Find where row H intersects with the 50 foot depth column and you find that your residual nitrogen time is now 66 minutes and your new adjusted no-decompression limit is now 14 minutes.

And so on. How to back into surface interval time using the dive tables In real life, reality often interferes with the best laid plans and time is an issue. How long would you have to wait on the surface? You find that your surface interval needs to be between and hours.

Follow row B to the right to Table 2 where it intersects with column G. Now you have to wait to hours between dives. See what a big impact the extra bottom time has on surface interval time?

Repetitive Dive -- The term "repetitive dive" refers to any dive made less than 24 hours after a prior dive. Letter Group -- As expained above, for repetitive dive planning purposes it represents the "Letter Group" of the amount of nitrogen that remains in your body after a dive. Residual Nitrogen Time RNT -- Represents, for repetitive dive planning puroses, the amount of nitrogen remaining in your body from a dive, ro dives, ade within the prior 24 hours.

It is the depth you could stay there if it were your first dive minus the residual nitrogen time. That number of minutes is used to find the letter Group after your next dive. The NAUI Dive Tables also remind that: Dives to less than 40 feet depth are treated as 40 foor dives Do not ascent faster than 30 feet per minute To maximize dive time, start with the deppest dive, and then make each repetitive dive shallower than the prior one. PADI Table 1, the No Decompression Limits and Group Designation Table, shows that the absolute maximum time you can stay at that depth without having to make a decompression stop is 55 minutes if you have enough air, that is.

You do that dive and come back up. Can you now just use that same table, get a fresh tank of air, and go right back down for a second look? Residual nitrogen after a dive See, the problem is that while science has determined that it is safe to ascend from 60 feet after 35 minutes -- "safe" meaning that nitrogen gets released at a sufficiently slow rate so as not to pose a danger -- it does NOT mean all the nitrogen that was absorbed into your body down there was released during ascent.

It essentially tells you how much nitrogen leaves your body over time. That is where the "Pressure Groups" come in. After your first dive you are in a certain Pressure Group, as shown in Table 1. That 35 minute dive to 60 feet put you in Pressure Group N.

Table 2 shows what Pressure Group you will be in after a certain "surface interval," i. So what the Dive Planner does is determine how much extra nitrogen is still in your body after a dive, and then convert that into "Residual Nitrogen Time," or "RNT. We follow "N" into table 2 and then find the column for a 30 minute surface interval. That would be column I. So now we flip the table told you it was a bit cumbersome and look at column I. Then we look at the cell where column I intersects with the 50 feet row.

There will be two numbers: 31 on top white background and 49 on the bottom blue background. The top number is your residual nitrogen time. The second number, 49, is your adjusted no-decompression limit, the time you cannot exceed on your next dive. So your total bottom time is now 61 minutes.

Flip the chart around and look at Table 1. As stated above, although you only stayed for 30 minutes at 50 feet on the second dive, you need to add the 31 minutes of residual nitrogen you still had in your system, i. If you now plan on waiting an hour and 15 minutes, and then go see that reef at 50 feet again, you find yourself in Pressure Group E. Flip the chart once again so you can see Table 3.

Find where column E intersects with the 50 foot depth row and you find that your residual nitrogen time is now 21 minutes and your new adjusted no-decompression limit is now 59 minutes. You find that your surface interval needs to be just minutes. Flip the chart and intersect column D with row N.

BLUR KRISTEN MIDDLETON PDF

IANTD Tables

Dive tables are used to determine how long you can safely stay under water at a given depth, both for the initial dive and for subsequent dives. To many aspiring scuba divers, Dive Tables are scary. And there are other formats as well. My suggestion is to use and understand one set of tables and stick with them. So what does a dive planner do? As explained in the "Physics" and "Physiology" sections, when we dive, our body tissues absorb nitrogen.

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Reading Dive Tables

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