2 incidents that occurred a week apart last summer

[DiverAmy]

Good questions, giantfan and racerx_. I didn't think I was going to be diving as deep as the dive turned out to be. I thought it would be 120 to the floor and didn't plan on diving to the floor. I misjudged the lack of depth the wreck itself had, I am not sure how to explain this, it seemed like a flat barge on the floor, not what I was expecting. I thought I would be able to hang around at the top of the wreck. I also didn't expect the Nitrox tanks to be close to 33%, another misjudgment. Oh, it was labeled 32% (for all that's worth), when analyzed it was over 32.5. I did figure out the MOD and my computer was kind enough to point it out to me as well. I set my computer to 1.6 out of sheer stupidity. I listened to a more experienced diver who told me that PADI's 1.4 was overly conservative. So, I made a number of mistakes to get to where I went. I am only blaming me. Live (thank goodness) and learn.

 

[racerx_]

Understood. From what I understand 1.6 is still the contingency depth. Just personally I wouldn't want to get near it as the risks far outweigh the benefits. Anyway, you made it through two pretty sketchy moments and can learn from em so thats good.

 

[DiverAmy]

I couldn't imagine ever taking that risk again. I have learned so much by telling these two stories and getting feedback. One of the first people to respond inspired me to do only a few minutes of research which led me to conclude that using 1.2 as a MOD and 1.4 as a COD might not be a bad idea, but exceeding 1.4 for a MOD could be a deadly mistake.

 

[Divedoggie]

My last nitrox dive the tanks weren't analyzing at what the sticker said they were supposed to be at so had to go back to the shop that filled it and figure out what was going on with the transmitter before Id dive it. The DM seemed completely unconcerned and if it wasn't for me pushing we would have kept diving. 6

Do you mean you had to go back to the shop to see what was going on with the analyzer? (You said transmitter.)

If you suspected the analyzer was not calibrated properly, then going back to the shop was smart. If the DM knew the analyzer was working properly, and the gas was still within the MOD for the planned dive, that might explain why he/she was unconcerned.

Ultimately, each diver is responsible for himself and has to be comfortable with the plans, the equipment, the gas, and the dives. Complacency can kill the most experienced diver, so it was probably good for you to have pushed to go back to the shop.

 

[TSandM]

One of the things that made a big impression on me, when I joined ScubaBoard, was a post by a very insightful man named Mike Ferrara (who doesn't hang out here any more, sadly). He said that, in his view, deep dives like the one you made are just better planned and executed as staged decompression dives. With the right training, the right gases, and the right dive plan, you actually get to spend meaningful TIME on the wreck, and do it safely and with a clear head.

I have never really understood the appeal of square profiles below 100 feet as rec dives. The bottom time is so minimal.

 

[DiverAmy]

TSandM, I am very interested in beginning to learn about that (staged decompression diving). Could you suggest some direction? Where does one obtain training?

 

[Jim Lapenta]

A number of agencies offer courses in staged deco. Also known as decompression procedures and often taught with an advanced nitrox class which teaches you how to use nitrox mixes up to 100% O2. Often called technical training. I have experience with two agencies for tech training. NAUI tech and TDI. Both have high standards for tech training and for tech instructors. They also allow the instructor to add valuable info and skills to the courses and to test on those additions. These are courses you can and will fail if you do not meet the requirements. You often start with an intro to tech class that introduces you to the gear, skills, and perhaps most important, the mindset of a technical diver. It may also serve to scare you off as there are no punches pulled if the instructor is good. One of the first things you do in a good intro course is look at the different ways you can get hurt or die doing these types of dives. This is done to impress how serious this stuff is. It should be done in ow class but that would not be good for many bottom lines.

Sent from my DROID X2 using Tapata

 

[racerx_]

Do you mean you had to go back to the shop to see what was going on with the analyzer? (You said transmitter.)

If you suspected the analyzer was not calibrated properly, then going back to the shop was smart. If the DM knew the analyzer was working properly, and the gas was still within the MOD for the planned dive, that might explain why he/she was unconcerned.

Ultimately, each diver is responsible for himself and has to be comfortable with the plans, the equipment, the gas, and the dives. Complacency can kill the most experienced diver, so it was probably good for you to have pushed to go back to the shop.

Oh yeah ha.. Analyzer.. The tanks were from the shop next door cause the Dec I dove with didn't have nitrox. DM wasn't concerned when the reading was different every time, sometimes higher sometimes lower and all over the shop and had no idea how to work the analyzer. Craziness..

Lynn & Jim interesting thought on the staged decompression dive, I'm gonna look in to that some more

 

[racerx_]

Would you necessarily have to have alternate gas mixes (deco bottles etc) to do a staged deco dive, or just plan and execute the correct deco stops along the way up. I'm referring to dives that would stay around 100-120ft or so

 

[TSandM]

You can do backgas deco, although the times get long fairly fast, which is why most people who go into planned decompression also accelerate their deco with higher O2 mixes.

You can also do the bottom time of a 120 foot dive on a light Nitrox mix -- I won't, and most of the people I dive with won't, because narcosis makes you dull at those depths, even if you don't feel drunk. For me, a 120 foot dive is a planned staged decompression dive, executed on 25/25 and using either 50% or 100% for deco.

Lots of agencies teach staged decompression. Many combine a class called Advanced Nitrox with one called Deco Procedures. Some have a class called Tech 1 (GUE & UTD do) that combines the two. There are differences in how agencies approach staged decompression diving. Some introduce helium immediately (GUE & UTD do) and some require you to take a further class called Trimix, and do not use helium until the dives are below 150 feet. Read standards and find class descriptions, and be very careful with your choice of instructor, because they are not all the same. I would highly recommend taking an Intro to Tech or GUE Fundamentals class (really, I'd recommend the latter in most cases) to get a view of how the standards for diving skills change, when you cross the line into technical diving.