Forgot to set computer nitrox mix, what a PIA

[Dr. Lecter]

I see your post has it's usual accuracy. I have no professional role in diving, major or minor and this is the basic scuba forum so I doubt too many tech computers are involved.

My sincere, if largely indifferent, apology - I confused you with another random string of letters user name who's a DM. In any event, the OP should not be lead to believe the problem he suffered (admittedly because he apparently can't be bothered to plan his dive or check his own equipment) is a necessary evil of dive computers.

If people want to buy trash dive computers that try to outthink the diver, they're more than welcome to do so. In fact, it seems to work fine for many divers. But that's hardly the only option.

 

[dumpsterDiver]

I was feeling great. I got on the boat, the seas were 1 ft, and I had my gear setup on my tank before we left dock. This is usually the time I set my computer and I completely forgot.

I'm doing a drift dive on Juno Ledge on a boat out of WPB. Max depth was 88ft and my average depth was 70ft. I've dove this profile many times, so I didn't freak out when I looked at my computer 25 minutes in and it said I had a deco obligation. I typically call the dive around 45-50 minutes, but opted to call the dive early (37 min) when I saw some other divers shooting their SMB. I ended the dive with 1200 psi.

On the SI, I was shocked that my computer completely locked me out. It wouldn't let me adjust anything that had to do with diving. So now it's going to just be a depth gauge and bottom timer on the 2nd dive.

I was diving solo this day, but hanging around other divers as to not be completely alone. So on the 2nd dive, I told the DM that I was going to hanging around him and surface when he does. He shows me that he has nothing but a bottom timer... My next thought was that the 2nd dive was going to be interesting . Again, it's a common profile I dive. I just planned to make it a shorter dive than usual.

My 2nd dive had a max depth of 91ft, but I averaged 68ft. I was avoiding the bottom unless I saw something cool since I had no visibility on my NDL. I'm not sure where everyone took off to, but the DM and I found ourselves together without anyone else. So we just went looking for stuff. After 35 minutes he signaled he was ready to go up. I figured it was as good a time as any so I surfaced with him. I surfaced with 1500 psi.

Anyways, back to the topic on hand, why does the computer lock you out? Why am I not able to fix the nitrox mix setting? Is it that users of the computers can't be trusted? That would be ridiculous. I would have been better served if I could have fixed the setting for the previous dive and set it up for the 2nd dive. FWIW, I'm diving with an Oceanic Geo 2. I couldn't even change the dive mode to gauge mode.

Thoughts?

OK I seriously read this post. I am not really sure why the computer went into deco. Are we to assume that it reverted to air when the diver was actually using nitrox? If that is the case, then the diver seems to really NOT have a clue about how to handle deco and how his computer will work.

He should understand that if the computer gives him a deco stop (even if it is a false one due to not knowing his mix) he really should have read enough of the manual to understand that violation of a mandatory deco stop is going to lock up the computer and make it worthless for the remainder of the day. That is the way all the computers I have function in the last 20 years...

So, he had tons of air left.. he should have just cleared the computer, by doing the deco it required and then on the next dive punch in the correct nitrox mix and go happily down the road. Rather than scream and yell and call him a DA, maybe we should just tell him to RTFM (I almost got banned for telling someone that once too)... and learn a little more about what the heck he is doing.

Now about the professional DM who is not using a computer. That is stupid buttttt people need to realize that if this DM has done these dives hundreds of times with no problems, he probably can do it again. People need to realize that some people get bent easily and some don't seem to get bent very often, even when they push it hard. My personal theory is that diving has a somewhat self selection process... the people that get bent easily stop diving or learn to dive conservatively.. and the others who dive 3-4 days a week ad do it for a living... well don't follow their profiles unless you have also tested yourself hundreds of times... (and even then it is stupid).

 

[MrChen]

Thanks for all the feedback guys.

I've ran the dive profiles through tables in the past. I've dove the profiles many times and I dove them more conservatively.

I knew the computer went into deco mode because I didn't program it for my actual mix. I made a decision to do my standard 3 min safety stop; hindsight is always 20/20 and I will consider the great advice given. I didn't know I'd be locked out of the computer afterwards, but I do now. Though I have read the manual and done the online training (several times), the fact that I'd get locked out didn't sink in.

I consider this a learning experience. I'm sure everyone remembers the first time their computer went into deco, whether by mis-programming or by error during the dive.

 

[Wookie]

Thanks. I didn't really have a deco obligation based on the profile and my nitrox mix. It was frustrating and disappointing to be locked out. Thanks for the no fly info. And I won't forget again, at least I hope not

Prove it. If you're smarter than your computer, go ahead and prove it. You didn't see if you had a deco obligation before surfacing, and you ignored visual and audible warnings. Then you ignored the lockout (which you bought the computer to give you advice, I expect), you made a second dive and you ignored the advice it gave you.

Now, your computer manufacturer punished you for those lapses. Your computer manufacturer thinks they manufacture a pretty fancy bit of kit, and that some might even consider it to be life support equipment. Personally, I think that the best computer is your brain and a set of tables, but that's beside the point. If you ran that dive on tables, you would find yourself (90 feet for 37 minutes) with a 3 minute obligation if you were diving 32%. I don't know why you were in deco after 25 minutes, but your computer must have been set improperly.

And you ask if computer users can be trusted?

My advice. Invest in a big boy dive computer, a Shearwater or a LiquiVision. They expect you to screw up, so they will not spank you like a petulant child when you do. They will tell you visually when you are in deco, when you've violated deco, give you credit for your surface interval, and let you right back in. They also let you reset your gas underwater, upsidedown, and while on the potty. Or all three if you can make it work.

I'm sure everyone remembers the first time their computer went into deco, whether by mis-programming or by error during the dive.

Some of us planned it. Followed our plan. But I get your point. I remember the first time my computer reset itself to 50% O2 and 79% nitrogen and started screaming at me at about 50 feet. I surfaced, took it off my wrist, threw it as far as I could. I expect it's still there. Somewhere offshore.

 

[Peter_C]

I'm sure everyone remembers the first time their computer went into deco, whether by mis-programming or by error during the dive.

NOPE, NEVER! My computer has never gone into deco, because I have never gone into deco. I have dove nitrox with a computer conservatively set to air before. Dove it as air and followed the computers suggestion of NDL.

Now I carry tables in my pocket and dive in gauge mode. Still haven't gone into deco...

You are still missing the point that you should have followed your computers advice, surfaced earlier, and possibly performed a longer safety stop. Unless you had tables in your pocket or ran the profile right before getting into the water, you are deemed as being unsafe. Sorry for being harsh, that is what asbestos underwear are for.

 

[KeithG]

I consider this a learning experience.

That is what scubaboard is all about. These threads also help thicken up your skin a bit.

I'm sure everyone remembers the first time their computer went into deco, whether by mis-programming or by error during the dive.

Nope - has never happened. I am not deco trained. Just like I am not wreck or cave trained. So I make sure I do not do any of them. It has been very easy to avoid all 3.

To add to your learning experience, to the best of my knowledge, there are multiple types of computers:
- ones that do not do deco: my old aladin sport simply said "deco" and then wanted you to make a deco stop of "i will not tell you how long until it is over" minutes
- ones that do deco, but will lockout if you do not follow their advice.
- ones that do everything with no lockout
- ones that will lockout for doing some other non deco related "violation" (suunto fast ascend)
One size does not fit all.

 

[rivers]

I'm sure everyone remembers the first time their computer went into deco, whether by mis-programming or by error during the dive.

I no longer dive a computer (strictly multideco generated tables and a bottom timer now), but when I did, I never unintentionally went into deco. In fact, I have never unintentionally gone into deco (i have gone into planned deco however).

Look, you learned a lesson.

 

[redacted]

I remember the first time my computer reset itself to 50% O2 and 79% nitrogen and started screaming at me at about 50 feet. I surfaced, took it off my wrist, threw it as far as I could. I expect it's still there. Somewhere offshore.

I dive some old computers so mine also do that reset after each EAN dive but they are also so old that they don't talk (a good thing). When I screw up and don't reset, I abide by the AIR NDL it gives me and manage the PPO2 manually (no lockout for O2 anyway). The only times I put my computer into deco, I was diving 2 computers with EAN. I set one to 21% so I could experience the deco condition on the computer, which I honored. On occasion, I dive somewhat aggressively; so I don't fool around with possible NDL violations.

 

[lowviz]

...//... Look, you learned a lesson.

Indeed.

So if it ever happens again, for any reason, you need a last-ditch fallback plan in the DC on your shoulders.

Plan: Immediately (upon determining that something has gone wonky) ascend slowly to 15-20ft and suck down all but the last couple of hundred psi. Then surface SLOWLY and orally inflate at the surface.

-always orally inflate when you are at the surface so that it becomes a habit. Should you ever end up there OOA, your inflate button won't be working and you don't need an extra surprise.

 

[drrich2]

A issue in the OP seems to be 'should a recreational dive computer, if deco. is violated under the data given it, proceed to not only advise against further diving for 24 hours but actually lock up and refuse to function, in a paternalistic attempt to force the diver to stop diving?

I don't believe so, but there's room for debate. Some degree of paternalism is standard practice in recreational scuba; that's why they check C-cards before taking you on charter boats. Liability risk management is big, of course, but that is rooted in the idea the operator had some paternalistic duty.

On the other hand, before I blast Oceanic for making a nanny state paternalistic big brother liberty-violating device, I have to consider this. A key function of a dive computer is to provide you NDL, for use as a margin of safety suggesting that if you stay within them, your risk is minimal. While it might be an overstatement to claim the computer & its manufacturer have a 'duty of care' to you in this regard, as people can get bent within NDLs, the Geo 2 is a recreational dive computer not designed for deco. diving, or for dive planning when deco. has been violated. If the device design doesn't allow for safe operation under the parameters given (within 24 hours of violated deco.), it is reasonable for it to not function rather than risk giving bad, dangerous info. (e.g.: NDL's on subsequent dives).

The question as to whether you should be able to go back and change the gas mix on a dive you've already done is an interesting one, and could be a nice feature.

Richard.