Accidental DECO and mild panic in a non tech certified diver.

[caruso]

Your computer should have been set at 1.4...your mix should have been 30%/121 ft as opposed to 35%/99 ft...

Disagree completely. As I've said before there is not one study or even a documented incident that demonstrates any sort of significant risk to diving with a computer set to P02 1.6 with a single tank, at depths at or less than recreational limits.

If you went over your NDL...you should have made a deep stop at 60 ft until your computer signalled you to ascend to 20 ft...

Did you read the first post on this thread? Sounds like you didn't. To repeat- my sister freaked out and ascended to 15 feet very rapidly, I felt the need to follow her as quickly as I could to make sure she was ok. Even though the rapid ascent placed me at some risk.

Your sister's computer should have been set at 1.4..

She was diving air. No need to change settings on a dive computer when diving air at recreational depths under normal conditions.

You should both have been slinging bailout at that depth...single AL 80's with no bailout at 110' is insufficient quantity

I carry a 19 cf pony bottle on most dives, including this one.

and 21% will require her deco obligation at 60' to be considerably longer than yours...which will likely lead her into an ''out of air situation''...

Not likely at all, shes got an extremely low SAC rate and had 0ver 800 psi at the end of this dive- this after a very long hang at 15 feet following the rapid ascent and clearing the DECO obligation at 10'.

Learn your tables...do not dive outside your training limits...suggest you thoroughly re-read your Basic NITROX...and make sure your computer is preset for the mix you are diving with...

Don't accrue a deco obligation if not trained...there is no risk versus reward...

W...

Who are you talking to? None of what you wrote there is even remotely applicable to me or the dive in question other than the obvious mistake made by my sister monitoring her NDL limits. If you're talking to me, I have no issues understanding "basic Nitrox" or "diving outside of training limits" . I do agree my sister has some remedial work to do in this area, and I have and will continue to pass on the more useful responses on this thread to my sister, in one form or another. Yours isn't going to be one of them.

 

[aquacat8]

True...but there are two problems with the "RTFM, dude" answer. First, hands-on practice trumps book learning. Second, manuals are often pieces of crap. (I'm an educator by profession, and I teach technical writing, so I speak from a position of expertise on both issues.)

Oh, I agree. Manuals are SO sucky, and sometimes so are computer interfaces. I have compassion for your sister. It must be scary having that screen show you something you don’t understand because you read it in a manual like 700 dives ago. Recently I was locked out of my geo2 with a frozen screen showing nonsensical numbers but it was only because I was freediving with it accidentally set to scuba. I thought the battery died. Fixed itself later. Need to review the manual again before scuba, but WTF was that?

If your sis had started diving on tables she might have had a different idea. Slowly ascend to 15 feet, then just hang at 15-20 feet and suck that tank almost dry of all that extra air she was carrying. Yeah people might have to wait for you, but isn’t that what Mike Nelson would do?

 

[chillyinCanada]

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Please Note: This forum has special rules. This forum is intended to be a "flame free zone" where divers of any skill level may share their incident without fear of being accosted. Please show respect and courtesy at all times. Remember that the inquirer is sharing a potentially embarrassing moment. This is a learning zone and consequently, any off-topic or overly harsh responses will be removed. We encourage people to share their near misses, so that we all may learn from little mistakes that could ultimately be costly.

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[aquacat8]

Oh I see you did do an extra long hang... just me not reading closely enough. Sorry. Yeah what else could you do? I really just wanted to sympathize with the scariness of an unfamiliar computer screen. Of course she did know what it meant, but it was scary because it meant deco. Yeah in a perfect world we’d all know our computers backwards and forwards, and monitor them flawlessly, but I don’t know about y’all, but I still get confused by my phone.

 

[Bob DBF]

If you went over your NDL...you should have made a deep stop at 60 ft until your computer signalled you to ascend to 20 ft...

If one follows the Veo 200 dive computer and ascends directly to the deco stop, there is no 60' stop, however the ascent rate to the surface changes from 60 fpm to 30 fpm at 60'. The computer shows the ceiling/ deco stop the diver should stop and maintain, in the OP's case it was 10'. I would not expect a 20' stop unless there was substantial deco. It does say you can deco a little deeper than the stop, however it will take longer.


Lessons from the incident:
1. Know your computer. Easier said than done, but I reread the manual on a regular basis.

2. Don't Bolt! As long as you have gas you can make a normal ascent to a depth where you can conserve gas and sort out the problem. Works for most issues.

3. Every diver should know when they go into deco, and how to get out. Making sure one stays within NDL is the best plan.


Good save.


Bob

 

[W W Meixner]

---

---

A ScubaBoard Staff Message...

Reminder to all Members

Please Note: This forum has special rules. This forum is intended to be a "flame free zone" where divers of any skill level may share their incident without fear of being accosted. Please show respect and courtesy at all times. Remember that the inquirer is sharing a potentially embarrassing moment. This is a learning zone and consequently, any off-topic or overly harsh responses will be removed. We encourage people to share their near misses, so that we all may learn from little mistakes that could ultimately be costly.

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Oh, I agree. Manuals are SO sucky, and sometimes so are computer interfaces. I have compassion for your sister. It must be scary having that screen show you something you don’t understand because you read it in a manual like 700 dives ago. Recently I was locked out of my geo2 with a frozen screen showing nonsensical numbers but it was only because I was freediving with it accidentally set to scuba. I thought the battery died. Fixed itself later. Need to review the manual again before scuba, but WTF was that?

If your sis had started diving on tables she might have had a different idea. Slowly ascend to 15 feet, then just hang at 15-20 feet and suck that tank almost dry of all that extra air she was carrying. Yeah people might have to wait for you, but isn’t that what Mike Nelson would do?

Disagree completely. As I've said before there is not one study or even a documented incident that demonstrates any sort of significant risk to diving with a computer set to P02 1.6 with a single tank, at depths at or less than recreational limits.



Did you read the first post on this thread? Sounds like you didn't. To repeat- my sister freaked out and ascended to 15 feet very rapidly, I felt the need to follow her as quickly as I could to make sure she was ok. Even though the rapid ascent placed me at some risk.



She was diving air. No need to change settings on a dive computer when diving air at recreational depths under normal conditions.



I carry a 19 cf pony bottle on most dives, including this one.



Not likely at all, shes got an extremely low SAC rate and had 0ver 800 psi at the end of this dive- this after a very long hang at 15 feet following the rapid ascent and clearing the DECO obligation at 10'.



Who are you talking to? None of what you wrote there is even remotely applicable to me or the dive in question other than the obvious mistake made by my sister monitoring her NDL limits. If you're talking to me, I have no issues understanding "basic Nitrox" or "diving outside of training limits" . I do agree my sister has some remedial work to do in this area, and I have and will continue to pass on the more useful responses on this thread to my sister, in one form or another. Yours isn't going to be one of them.

If one follows the Veo 200 dive computer and ascends directly to the deco stop, there is no 60' stop, however the ascent rate to the surface changes from 60 fpm to 30 fpm at 60'. The computer shows the ceiling/ deco stop the diver should stop and maintain, in the OP's case it was 10'. I would not expect a 20' stop unless there was substantial deco. It does say you can deco a little deeper than the stop, however it will take longer.


Lessons from the incident:
1. Know your computer. Easier said than done, but I reread the manual on a regular basis.

2. Don't Bolt! As long as you have gas you can make a normal ascent to a depth where you can conserve gas and sort out the problem. Works for most issues.

3. Every diver should know when they go into deco, and how to get out. Making sure one stays within NDL is the best plan.


Good save.


Bob

Hey Bob...

My computer...will advise when NDL has been surpassed...and automatically stops you at a 60 ft ceiling...and depending on the time the NDL was surpassed...puts you in a count-down at 60' until stop obligation has been met...

I don't know if this system is typical...but I like the ''safety factor''...

From what I've been reading on SB...deep stops are no longer in vogue...but I like it...and with the rebreather there's no gas shortage concern trying to push you to the surface...

Best...

Warren

 

[Bob DBF]

My computer...will advise when NDL has been surpassed...and automatically stops you at a 60 ft ceiling...and depending on the time the NDL was surpassed...puts you in a count-down at 60' until stop obligation has been met...

I don't know if this system is typical...but I like the ''safety factor''...

I don't know if any computer is typical since there are so many different makes and models. The Veo 200 is a discontinued Oceanic running DSAT and is just this side of the Orca Edge as far as conservatism. I used one for years till it quit and I couldn't get service.

From what I've been reading on SB...deep stops are no longer in vogue...but I like it...and with the rebreather there's no gas shortage concern trying to push you to the surface...

Each to his own, I might be persuaded but I don't spend much time in deco so I stick to my old ways.


Bob

 

[Rechno]

why would you switch to air just because dive partner is on air? Can they not monitor their own NDL time? I mean thats pretty scary if they cant. Also what if you are at about 100 ft and you both see something crazy spectacular and your partner goes down to 130 ft and you are on 32 nitrox? you may forget as you put your computer on air and when you look at it everything looks okey dokey..... you could easily end up putting around at 130 for a few minutes on 32 and maybe nothing happens but i wont do it

As I said, I see it as an option, nothing mandatory. It all depends on the circumstances of the dive and especially the buddy (what I know about him, what I have seen and my gut feeling). With my regular buddies I would not do it, because I know that they monitor their NDL. For dives that are not simple " 10-15m and looking at fish"-dives we plan our runtimes anyway.
But the whole thread started because a buddy was obviously not able to monitor her NDL. And with instabuddies I might rather err on the side of caution.

Concerning the aspect "Also what if you are at about 100 ft and you both see something crazy spectacular and your partner goes down to 130 ft and you are on 32 nitrox":
a) I can set a depth alarm on my computer. So even if I would set it to air, I could still set the alarm for the Nitrox MOD... which might be a wise thing to do.
b) I trust myself, that I know what mix I am diving after I checked everything and prepare for the dive. When planning a dive I tend to take the mix and the respective MOD into consideration before I hit the water.

Again, I never recommend the practice to set the computer to air instead of nitrox and I never said, that I tend to do it. I just stated under what circumstances and for what reason I see it as a viable option.

 

[Gareth J]

why would you switch to air just because dive partner is on air? Can they not monitor their own NDL time? I mean thats pretty scary if they cant. Also what if you are at about 100 ft and you both see something crazy spectacular and your partner goes down to 130 ft and you are on 32 nitrox? you may forget as you put your computer on air and when you look at it everything looks okey dokey..... you could easily end up putting around at 130 for a few minutes on 32 and maybe nothing happens but i wont do it

Personally, I own 4 dive computers. 2 Suunto's, 1 OSTC, and 1 AP (part of the rebreather).
In normal circumstances I always dive 2. This is normally the AP (CCR), and the OSTC. The OSTC is set to 3 gases. I can switch between the bottom mix, an intermediate mix and a rich mix for decompression. So I can run down any compulsory deco on the OSTC by switching mixes, the OSTC gives me a (limited) backup to the CCR computer (with a hard table and bailout table).
Most of my diving is with OC buddies. I regularly set the OSTC to match the bottom mix of my buddy. If I'm lazy, I'll leave it set to air. It gives me a feel for my OC buddies decompression requirements thorough out the dive - reducing the risk of an unpleasant surprise at the end of the dive.

If I'm on OC, I'll run the OSTC and a Suunto, the OSTC becomes my primary instrument.

I also spend a lot of time in the water with students, new divers, and unknown divers. In these cases, one computer will be set to match my buddies bottom gas (and deco gas - if they have deco gas).
If I have a newer diver, or student I will often lend them one of the Suunto's.

With respect to overshooting MOD - How would you do that? Irrespective of the computer setting, I know the MOD of all my gases. Be they Bottom gas, travel gas, or deco gas. When I started using Nitrox, we only had air computers.
MOD is about dive discipline - you know what that is going in, and you don't break it.
There are only two golden rules with Nitrox
1. Check your mix before the dive.
2. DO NOT exceed the MOD.

If you are not prepared to do 1 and 2 then you shouldn't dive Nitrox.
When I did my original Nitrox, it was a compulsory fail if you exceeded any MOD during the diving (even fictious MOD's set by the instructor). All MOD's where set shallower than the site.
Similarly, when we used to teach Nitrox by actually doing dives as part of the course. It was an instant fail if you exceeded the MOD. We intentional set artificial MOD's and mixed them between the group. Each diver had to watch his/her depth, because other divers potentially would draw you beyond your limit.

My Trimix course, one section of the wreck was below the MOD, the shot was on that section. We had to put jump lines in to do the hop midwater to the section we could dive. Failure to stay above the MOD, was a course fail.

Dive computers are tools, they do not solve bad dive practice. Exceeding the MOD is bad dive practice. As is exceeding the agreed/planned bottom time (and depth).