TDI Decompression Procedures

[amascuba]

I'm looking for some information so that I somewhat know what to expect. I'm taking the class and doing my first two check out dive in July. I've read the book three times, which has some decent information about the physiology and decompression in general, but over all the book doesn't go into as much detail as I would really like. I know that every instructor is going to be different in how they teach the class, but are there any skills and/or procedures that are taught during the class or is this class just a basic this is how you plan and execute a dive that requires decompression stops?

I'm most likely going to be taking advanced nitrox from the same instructor and we have talked about using 50% for accelerated decompression during the second two check out dives, which are going to be deeper dives than the first two dives. I've got the advanced nitrox book and it certainly focuses more on the physiology and oxygen toxicity. It should be an interesting class.

I guess what I'm really looking for are other peoples experiences from their classes and how they viewed them. Thanks!

 

[Mark Vlahos]

I took the TDI Advanced NITROX and Decompression classes together a couple of years ago. For me, it was my first time in doubles, my first time with a separate decompression cylinder, my first actual decompression dives, my first time in a back plate and wing.

My instructor had me carrying two decompression cylinders later in the class, and he had me practice handing them off, setting them down, and picking them up. This may seem simple, but there are issues of added or removed weight and how that affects your bouyancy. Of course the doubles had a huge impact on my bouyabncy and trim. It was also the first time I inflated or "shot" a lift bag from depth. This seemingly simple task is a lot harder than you might think it should be, get ready to be humbled.

Of course there is the whole planning and execution thing, which should not be diminished in any way. There are actually quite a few things that you will be doing that will keep you very busy for the next several dives.

In my opinion the book was pretty basic with regard to the things you have outlined and even less informative about the things like shooting a bag and the issues surrounding bouyancy and trim.

You should have fun in the class, so be ready to learn and be ready to make some pretty decent mistakes. All in all you should get LOTS of really good information from this class. I considered my Advanced NITROX and Decompression Procedures class to be a real "Advanced Diving Class" and my AOW to be only a continued basic class.

Mark Vlahos

 

[DA Aquamaster]

I also took deco procedures and advanced nitrox a couple years ago. I had been diving doubels for several years prior to the course, it was no where near my first deco or accellerated deco dive, and it was obviously not my first time shooting a bag, but I needed the card so I took the course.

My course covered the same ground as Mark's with much time spent handing off stage bottles, sharing gas, shooting bags, determining SAC rate, doing accellerated deco with 50%, and repeating these skills on every dive.

Max depth on the checkouts was 150' in some very chilly 35 degree water.

I agree the TDI texts are a good on theory etc, but are a little weak in their coverage of in-water skills and our instuctor used some supplemental materials to address that deficiency.

If possible, it's well worth it to get some doubles experience and work out the weight and trim issues prior to taking the course. Your instructor will no doubt give you some configuration assistance and suggestions, but you will be ahead of the game if you are at least semi comfortable with doubles when you arrrive. The time you don't have to spend in the water adjusting trim and getting comfortable in doubles can then be well spent refining the other skills. With no doubles experience and with poor trim, you will be much more heavily task loaded during the dives and will not learn quite as much as you would otherwise.

 

[Diesel298]

those cflasses go hand in hand and are generally tought together.
deco proceedures with out advanced nitrox, is called extended range

 

[DA Aquamaster]

those cflasses go hand in hand and are generally tought together.
deco proceedures with out advanced nitrox, is called extended range

They are usually taught together and when taken together, the diver is certified to 150 ft.( although these two courses together used to certify you to 170'.)

And now it is really confusing as they say that deco procedures by itself certifies you to 150' unless taken with Advanced Nitrox, Extended Range or Advanced Wreck Courses, but does not specify any depth beyond 150'.

Extended range is a different course that teaches essentially the same thing as the combined courses, but certifies you to 180'.

 

[H2Andy]

when you guys say these courses "certify you" to 150 or 180 feet, do you mean
you take the class with the understanding that you will not dive beyond those depths?

or are those depths recommendations?

 

[Mark Vlahos]

when you guys say these courses "certify you" to 150 or 180 feet, do you mean
you take the class with the understanding that you will not dive beyond those depths?

or are those depths recommendations?

The TDI Decompression Procedures card says right on it, "Qualified to conduct dives for planned staged decompression to 150 fsw/45msw."

The TDI Advanced Nitrox card says, "Qualified in the use of 22% to 100% nitrox"

The TDI Full Cave card says, "Trained to cave dive to the standards of guideline, air management, depth and light rules established for safety in the overhead environment to a depth of 130 ft."

Together if I dive within the limits of my training I can do a planned staged decompression dive to 150 fsw and use pure oxygen as a decompression gas on that dive. In my class we used a total of three gasses, back gas and two different deco gasses.

It should be noted that technically I am able to do decompression in open water to a depth of 150 feet, but only to 130 feet in a cave. This is because the TDI deco class is not an "overhead environment" classification, but the deco section of full cave allows me to do planned decompression dives in an "overhead environment" to a depth of 130 feet. I personally view this as a quirk of the way they organize the instruction and not because there are different skills needed, sort of a clerical void.

Mark Vlahos

 

[Diesel298]

when you guys say these courses "certify you" to 150 or 180 feet, do you mean
you take the class with the understanding that you will not dive beyond those depths?

or are those depths recommendations?

Yes. just like a padi deep diver specialty is for 130 FSW
extended range is for air diving and deco on air for 180 FSW and deco proceedures is 150.. i personally thing that should be the other way around.
extended range was commonly tought with entry level trimix also,,,
but now-a-days the norm is adv. nitrox deco tought together and if somone wants a extended range cert its EZ to presuade them into entry level trimix insted..
with that you by default a more qualified diver (or more certified dive) w/o entended range, and you save yourself taking a extra class and spending extra money.
i think advanced nitrox is useless w/o deco, and deco w/o adv nitrox is useless because its basically a mini extended range. AND the TDI boos for both of those classes seem a little dependant on one another.
It would be simpler for all to just combine the classes to one...
but that would be taking a extra 12 bucks out TDI's bank acount...
SOLUTION: combine the 2 book s into one.. and charge a extra 12 bucks for the book

 

[DA Aquamaster]

I agree with you that Extended Range is pretty useless as a course and that it makes a lot more sense at that point to skip it and take Entry Level Trimix. Diving to 180' on air is more than a little stupid and you gain basically nothing useful compared to the Deco Procedures/Advanced Nitrox combination.

And since you don't need to take Extended Range as a pre-requisite for Entry Level Trimix, it is pretty much an anachronism.

 

[amascuba]

I'm in the same boat with Extended Range. Unless they teach you alot of skills that aren't taught in advanced nitrox/decompression procedures; why would you take extended range, just so that you can go an extra 30 feet on air? If I decide that I want to go deeper I will probably take a trimix class and skip the Extended Range class all together.

Beside's that, It almost sounds as if my instructor is combining Extended Range/Decompression Procedures/Advanced Nitrox into my class. The way he described my check out dives are:

Dive 1 & 2: 80 foot decompression dive with out a any accelerated decompression.
Dive 3 & 4: 180 and 150 foot decompression dive with 80% and 50% decompression dive. He basically said that I'm going to carry a stage with the 50% and the 80% is going to be hanging at 30 foot from a surface buoy.

The only class that I've actually paid for so far is Decompression Procedures. My instructor is in a city that's a couple hour's away. Basically his pre-requisites for the class were to be atleast "Rescue Diver" certified with atleast 100 dives and he wanted to dive with me and get to know me a little before he would actually let me take the classes. His standards seem to be some what higher than what's actually listed on the tdisdi.com website, which is cool. I had never met the guy before I called to inquire about the classes, but so far I'm impressed that it doesn't appear that he's just giving out cards.

I'm looking forward to the class though. We are going to do the first two dives and the classroom portion on July 21 and then come back a week or two later to do the second two dives. The second two dives are going to be in a hole (technically a lava tube) that I've never been in before. It's on private land and the owners are pretty picky who they let dive on it. It's supposedly 300+ feet deep, but I've never actually talked to anybody who's touched the bottom. I've only talked to people who have been to 240 feet before they thumbed the dive. Altitude at this location is 4600 feet, so at those depth altitude correction becomes a wide margin.

Thanks everybody for replying. It's been an interesting read so far. Keep it coming if anybody has anything else to add.