Deco Proc Course Gear Requirments

[Scuba Cowboy]

Since the OP is not a tech diver how does he know the single tank is not the optimum choice? That was probably why the question was posed here. It should be the responsibility of the instructor to inform him of that. There are applications when a single tank might be the best choice.

Please enlighten me as to which application, on a decompression dive, a single tank would be a better choice than doubles. I cannot think of one. And I believe this OP is like others I've talked to, he knows the vast majority are doing deco in doubles, but is for some reason looking for permission to do it in a single. Whether its a money issue, a physical ability issue, I don't know, but its been my experience that people who ask this question are looking for a way to try something they are not ready for. This person has probably already talked to an instructor and been told they need doubles. Someone then told them standards allow singles and thats why I think the question was asked. My post was intended to help inform him why some instructors require doubles for this class.

 

[wedivebc]

Please enlighten me as to which application, on a decompression dive, a single tank would be a better choice than doubles. I cannot think of one. And I believe this OP is like others I've talked to, he knows the vast majority are doing deco in doubles, but is for some reason looking for permission to do it in a single. Whether its a money issue, a physical ability issue, I don't know, but its been my experience that people who ask this question are looking for a way to try something they are not ready for. This person has probably already talked to an instructor and been told they need doubles. Someone then told them standards allow singles and thats why I think the question was asked. My post was intended to help inform him why some instructors require doubles for this class.

Well you are sure making alot of assumptions of the OPs intentions and actions since I don't know the person myself I won't presume to know why he wanted to know this information.
Single tank decompression diving is not appropriate for the environment I dive in but there must be some application for it otherwise why would TDI have in in their standards?

 

[JeffG]

Well you are sure making alot of assumptions of the OPs intentions and actions since I don't know the person myself I won't presume to know why he wanted to know this information.
Single tank decompression diving is not appropriate for the environment I dive in but there must be some application for it otherwise why would TDI have in in their standards?

I've heard some tech diver discuss using a Single tank back gas in conjunction with stages to do deco diving in tropical locations where doubles cannot be rented.

 

[Blue Quaker]

I've taught the Adv. Nitrox/Deco combo program to a couple of students that wore HP large capacity steel singles with H valve and a 40 cuft for deco gas. They were small (5' 6"-110lb women) who had a really low SAC rate, and didn't want the "aggro" of hauliing doubles around, but wanted the knowlegde and skills to dive beyond the no-stop limits at recreational depths...not everyone takes Adv. Nitrox/Deco as a stepping stone to other more technical courses.
Cheers,
Norman H.

 

[Steve SDI/TDI HQ]

Just a quick note here. Since we have members teaching our programs around the world, in every conceivable type of environment, I'm unlikely to come close to hitting all the applications in which a single cylinder with H or Y valve would be an acceptable choice over a set of doubles... but I can think of several.

Some years ago, when I was part of our training advisory panel, we polled members asking at what stage in diver development they began to insist on the use of doubles. Many very experienced instructors argued convincingly that a single cylinder with redundant first stages gave an acceptable level of security for students enrolled in a TDI Decompression Procedures course and so we included this gear package as an option in the standards for this course.

In keeping with our general standards and code of conduct, ALL Technical Diving International instructors are free to "add" to course outlines to make them more suited to local conditions and mores. As posted early, most instructors in "mainland" USA and Canada do expect students to dive manifolded doubles. However, completing a course wearing a large volume single as per standards, does not mean the course is lacking anything or that it turns out a sub-par diver. Wearing a single high volume cylinder with an H or Y valve rather than doubles is the choice of many very experienced divers. For example, I've dove on a number of occasions with Bret Gilliam (the founder and one-time owner of TDI) off the coast of Florida and in the tropics on open-circuit and he habitually uses a single... I used one as well. I don't think Bret (or I) fall into the inexperienced diver category, and neither of us is given to taking shortcuts.)

I am not sure what the intentions are of the original poster. The only safe assumption is that they are curious about gear configuration for a TDI course. I am pleased to see so many people posting helpful information on that assumption.

Weight of gear was mentioned as perhaps being an issue and that brings to mind something that has not been mentioned. I have taught this class on several occasions with students (and instructor) wearing manifolded six litre (45 cubic foot) cylinders. This is a very light option.

 

[Scuba Cowboy]

"Just a quick note here. Since we have members teaching our programs around the world, in every conceivable type of environment, I'm unlikely to come close to hitting all the applications in which a single cylinder with H or Y valve would be an acceptable choice over a set of doubles... but I can think of several."

I'm sure a big single is an acceptable choice, I've done deco in one myself, but not a better choice over doubles. There is always that slim possiblity of a valve o-ring or burst disk failure that would cause a huge problem. I agree totally on a small set of doubles, I used to dive double 72's which are probably lighter than some singles. In the tech world, we preach redundancy and a single tank does not provide it.
My bad for assuming what the OP is thinking, just going off what I have experienced when this question is asked. I'm officially off the soap box now

 

[Dive-aholic]

Steve, being that TDI has been so flexible, why is shooting a bag required in the technical courses? All of my training was done in caves, yet we had to take lift bags with us and shoot them in the basin to meet the standards of the course. Is it possible that this standard could be revised to allow for cave divers not to have to complete it?

 

[Doppler]

Steve, being that TDI has been so flexible, why is shooting a bag required in the technical courses? All of my training was done in caves, yet we had to take lift bags with us and shoot them in the basin to meet the standards of the course. Is it possible that this standard could be revised to allow for cave divers not to have to complete it?

Hi Rob: Thorny issue

When our standards and skillsets were first drawn up, TDI did not have a cave program and many of our ITs and Instructors... those with cert numbers in the low double digits... worked in areas where blowing a bag was either required (such as live boating wrecks in Florida's Gulf Stream) or good solid insurance (such as off the NorthEastern Seaboard). The skill stuck. Personally, I'm glad it did because one day you may be diving off Pompano or the Keys and that skill will prove useful.

Larry Green (who heads up our Cave Diving Training Panel and is our cave instructor-trainer as well as being the training officer for NACD), much like you asks this question and jokes that he has no idea what a liftbag or DSMB is for, but when he and I have discussed this, admits that having a student fly a bag in mid-water does test buoyancy control. He also on occasion, when the seas are calm, dives in the ocean and is glad he can at least throw a bag up to the surface if need be.

I am no longer a member of the Training Panel and so cannot give you a definitive answer on if there is a change to this skill in the works... I know that Sean Harrison (our v-p of training and membership services) reads this forum and he may be able to chip in.

In the meanwhile, have fun and dive safe.

 

[=C=]

Please enlighten me as to which application, on a decompression dive, a single tank would be a better choice than doubles....

Deep wreck where doubles are tooo wide for the passageways...

 

[Fair Weather Diver]

After reading this thread I figured it was time for me to give you TDI’s perspective and logic as to why we require the shooting/floating of a bag in the Decompression Procedures course.

TDI’s logic behind this particular skill actually transcends a lot of course standards and that is, we want divers to learn skills for various environments. Because a diver comes to a course with a single goal in mind does not mean that is all they will ever do. How many divers have you heard say “all I want to do is get open water certified”, only to find themselves hooked and wanting to learn more? A year later they are enrolled in a cavern through cave course or a wreck course. The standards are drafted to create a well rounded diver, just like the educational system. Remember when you got out of high school and said “I am never going to use physics in my life” and think about how much you use that now while diving?
I agree that shooting a bag in an overhead environment is not only environmentally unfriendly, it could be dangerous. This skill must be conducted in a non-overhead area, such as a basin when teaching in caves or on the weather deck when conducting wreck dives.

For various reasons, training dives are and can be conducted in predictable environments like a basin, cave, connote. Doing training dives in these areas avoids the delays of weather, sea conditions, etc but the diver still needs to know the skills to be a proficient diver wherever their diving adventures might take them.

The skills and knowledge gained during the Decompression Procedures course is commonly used while wreck diving and shooting a bag is almost a mandatory skill in a lot of these locations.
I hope I have answered the question sufficiently and that my answer has provided some insight as to why it remains in our standard.

Safe diving
Sean Harrison VP training and Membership services