OK to Bounce Dive to 220 Fsw as...

[The Chad]

I'll chime in with everyone else. Pretty much any dive other that a SAT dive is a bounce dive. Why this clown would even suggust it would be okay to do it is beyond me. There are plenty of videos (as someone pointed out) about single tank cowboys taking on the Blue Hole. Deep diving is done with a calculated risk. The instructor should have just refurred them to more advanced training other than AOW or simpy said "take a revolver put one bullet in spin it, put it to your head and pull the trigger... and then repeat. See how many times you get away with it"

 

[brockbr]

3. The PO2 is too high at 220 ft (1.61). 1.4 is the maximum allowable P02 for the working portion of the dive, and for good reason. Some people suffer oxtox at 1.5, other at greater than 1.8. Deco PO2 is allowed to reach 1.61 (02 at 20fsw) but some people do not like to breath at such high P02's for the same reason. I have personally experienced oxtox symptoms at 20fsw breathing 02, but that is a different story for a different time. Hyperbaric chambers may exceed 1.61 but they do it in a CONTROLLED environment while controlling a number of variables.

I would NOT condone the depth on air (for the untrained), or the use of o2 above 1.6, BUT, let's not add disinformation - There are extremely few cases (and most are undocumented) of people toxing at 1.5.

Firstly, the Navy used a standard of 2.0 for a long time for normal oxygen exposures with good results.

Secondly, I spent a good deal of time at Duke university during a diving study I participated in. It is very typical (as mentioned elsewhere in this thread) to see O2 exposures of 2.0 or higher. I was told, in no uncertain terms, that people don't tox at 2.0, unless they are exposed for a long amount of time.

There are many, many other factors in doing dives like the one mentioned safely (with O2 exposure being at the bottom of the list, if not even factored since we are talking ~1.6 whch has an acceptable exposure of 45 minutes):
1) Water temp? A cold dive to 130' on air can be just as bad as a warm dive to 200'

2) Visibility? Is it gin clear or 12"? At 12", a 130' dive on air isn't a boatload of fun.

3) Current? Is there any? Descending down a wall into zero current is nothing like fighting to drop down an anchor line in a 2 knot current.

4) Equipment? You DO have dual first and second stages, right? At 220', a person with an elevated sac of 1.0 will blow through an AL80 in 10 minutes. Doing a dive like this in anything but doubles isn't very bright.

5) Training? No matter what, you will incur a decompression obligation. Do you have the proper training and equipment to decompress properly?

6) Team? Who comprises the team, and what is their experience?

7) How do you and your teammate respond to narcosis?

I could go on and on - My point is that an air dive to 220' made in a blue hole (no current) with 200' of viz, 85F temps, in doubles and a suitably configured teammate would be infinitely easier than dropping into the U-869 on a bad Atlantic day in a single.

Also - You do NOT turn into a pumpkin when the O2 exposure hits 1.61

b.

 

[udtfire]

i recover bodies as a job skill we refer to this as call volume, my vote is NO

 

[zaberman1]

I would NOT condone the depth on air (for the untrained), or the use of o2 above 1.6, BUT, let's not add disinformation - There are extremely few cases (and most are undocumented) of people toxing at 1.5.

Firstly, the Navy used a standard of 2.0 for a long time for normal oxygen exposures with good results.

Secondly, I spent a good deal of time at Duke university during a diving study I participated in. It is very typical (as mentioned elsewhere in this thread) to see O2 exposures of 2.0 or higher. I was told, in no uncertain terms, that people don't tox at 2.0, unless they are exposed for a long amount of time.

There are many, many other factors in doing dives like the one mentioned safely (with O2 exposure being at the bottom of the list, if not even factored since we are talking ~1.6 whch has an acceptable exposure of 45 minutes):
1) Water temp? A cold dive to 130' on air can be just as bad as a warm dive to 200'

2) Visibility? Is it gin clear or 12"? At 12", a 130' dive on air isn't a boatload of fun.

3) Current? Is there any? Descending down a wall into zero current is nothing like fighting to drop down an anchor line in a 2 knot current.

4) Equipment? You DO have dual first and second stages, right? At 220', a person with an elevated sac of 1.0 will blow through an AL80 in 10 minutes. Doing a dive like this in anything but doubles isn't very bright.

5) Training? No matter what, you will incur a decompression obligation. Do you have the proper training and equipment to decompress properly?

6) Team? Who comprises the team, and what is their experience?

7) How do you and your teammate respond to narcosis?

I could go on and on - My point is that an air dive to 220' made in a blue hole (no current) with 200' of viz, 85F temps, in doubles and a suitably configured teammate would be infinitely easier than dropping into the U-869 on a bad Atlantic day in a single.

Also - You do NOT turn into a pumpkin when the O2 exposure hits 1.61

b.

Thanks for the info but I wasn't suggesting EVERYONE toxes at 1.61, I was implying there are other factors at work. For instance, my almost tox experience occurred on a VERY rough day with strong currents after a long dive on the hydro atlantic. Given the variables at play, 1.4 for working and 1.61 for deco seem to be safe bets, didn't think I was giving any misinformation.

 

[AfterDark]

How deep can you dive? I'll go all the way to the bottom if I don't stop myself.

 

[DCBC]

No the discussion was started as a fellow diver asked me what would be the issue with a bounce dive to 220?
I have had many deep dives and he was asking the possible dangers, I wanted to advise him that it isn’t the Partial Pressure that is the danger (at least not at 1.6) it is the narcosis and to attempt anything you are not trained for is risky at best.
I said along with training you must be in good shape as physiology is a great factor in many things on a dive.
Also adipose cells can harbor more micro-bubbles and being overweight doesn’t help.
Not that overweight divers shouldn’t dive so don’t get offensive if you are over weight, it is a fact cardio is a major factor in any activity.
Also the more efficient the cardio vascular system the more efficient off gassing.

Anyways my thoughts were on narcosis and getting in shape will increase your capabilities should the need arise.

As you double posted this comment on the other thread on Nitrogen Narcosis, please see my answer there.

As far as the Instructor's suggestion is concerned:

1. He's an idiot. Such a suggestion makes me question the competence of the "Advanced Diver" program that he ran.

2. The "Sport Diving" depth limit is 130 FSW. No diver without technical, commercial or Navy training has any business exceeding this depth.

Your answer to the newly certified "Advanced Diver" should be mitigated by the fact that you're not a commercial, military or technical Instructor and would be best to refer them to one. In other words: "Don't do there, too dangerous, seek appropriate instruction before any attempt."

 

[BDSC]

I hear the typical dive there is ~130ft to get to the stalactite structures on the underside of the ledge. That's precious little bottom time at NDL, not to mention rock bottom reserves. Don't think I'd do that dive.

Funny, the left sidebar banner is screaming "BELIZE - BLUE HOLE BARGAIN -SAVE $700" to me as I type.

We did the Belize Blue Hole this past August and I went to about 144 ft to be able to swim through the stalactites. We had several new divers (10 to 20 dives) with us and some were a little nervous about the depths but all ended up doing the dive. Folks were given an option to hang out a lot higher if they wanted. No pressure at all to do the dive from anyone. The dive master lead the dive but was constantly looking and checking with the newer divers to make sure they were OK. I think the total dive ended up being maybe 20 minutes or so. After the dive all the new divers were glad they did it and said it helped them overcome some of their fears of diving to some deeper depths.

 

[brockbr]

Thanks for the info but I wasn't suggesting EVERYONE toxes at 1.61, I was implying there are other factors at work. For instance, my almost tox experience occurred on a VERY rough day with strong currents after a long dive on the hydro atlantic. Given the variables at play, 1.4 for working and 1.61 for deco seem to be safe bets, didn't think I was giving any misinformation.

Sorry - The only mis-info I was referring to was the statement about people toxing at 1.5 - That simply isn't the case. As I mentioned, there are very few cases of toxing at 1.5, and most (if not all) are anecdotal and undocumented.

Even then, some were on CCR where the pO2 wasn't exactly reliable - This could easily be due to moisture on the cell face (the most common problem) causing them to read low (and thus the loop is higher than shown), or current limited cells.

 

[zaberman1]

no prob, thanks for the clarification!

 

[DCBC]

As I mentioned, there are very few cases of toxing at 1.5, and most (if not all) are anecdotal and undocumented.

I know what your trying to say, but a PPO2 of 1.5 is lots of PP to tox. There have been numerous documented cases in the commercial diving industry.

There is another variable in the formula and that's time of exposure. What doesn't hurt you at 10 minutes, can kill you in 2 hours. It's also accumulative with repetitive dives. There are also individual tolerances to PPO2, so there's a good reason for planning a 1.4 PPO2 maximum.