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

[Diving Dubai]

I wish more people would take Tec 40, Extended Range, AN/PP etc. I also wish the agencies would change they way they're marketed moving the basic Deco course away from the mysterious (to most) "Tec" and back to the mainstream.

I wish like BSAC basic backgas deco procedures were taught as part of the recreational curriculum, probably replacing the "Deep" speciality.

I personally don't' formally plan most dives - equally I don't' just jump in on a wish and a prayer. I know the gas mix I'm carrying is suitable for the site - it maybe too lean but I have options. I know my gas volume will allow me a 60 min dive with a healthy reserve.

I have of course previously actually calculated all of my requirement (inc rock bottoms), so I know my choices on paper are good, and that's validated by numerous dives using that data.

So a general dive it's "just" a case of making informed decisions underwater calculating the impacts of going and staying deep or perhaps fighting current, then being able to adjust my profile on the fly to ensure I don't overstay the max time, or encroach into my reserves.

There should be no difference in what I do on dives that may have a max depth of 50m/160' to a simple 18m/60' on an AL 80 with 21% the basic principles are all the same

 

[NAUI Wowie]

If you were going to dive with your sister as a buddy, then you should have set your computer to air OR very carefully monitored her deco status on a 110 ft dive. After 30 minutes, if you had any sense of diving, you would know that she would be in deco or close to it. This is a significant diving error in my book.

In addition, I would not have done what you did with your sister on the ascent. The OP indicates she took off and presumably started to ascend rapidly. In that situation and finding her at 15 feet with a 10 foot ceiling, I would have confirmed adequate gas supply and then I would have her descend to 20 feet or, at least stay at 15. Since she apparently already did an accelerated ascent and had a short deco, I would have cleared it at 15 or 20 and then done a safety stop at 15-20. The deco probably clears a tiny bit faster at 10, but I personally would have encouraged her to stay a little below her deco ceiling if there were no time, gas supply or other issues of significance.

This is really a pretty significant lack of awareness of basic diving protocols. If you are going to do a deeper dive with someone who has the capacity to go way into deco (due to exceptionally low gas usage) and the two divers are using vastly different mixes - you gotta be looking at her computer during the dive.

If you are diving nitrox please do not ever set your computer to air thats just wrong. Second point his sister has and had over 700 dives.

SEVEN HUNDRED DIVES

No one needs to babysit a diver with that many dives who also surfaces with the most air every dive. she probably surfaced with the most air on this dive too..... she just did not understand the deco obligation....would she have died at any point? no . was it a very interesting story and one that will educate people? yes. did the brother need to change anything or do anything different? No.

Basically his sister kind of I wont say panicked but she freaked out over her computer.

Was his sister out of control or a danger to herself or others? No.

was she panicked in the real diver definition? no not by a long shot and not with her 700 dives and just her computer giving her info.

was she freaked out about it? oh yea and thus did her best to get to the surface.

its a learning experience for her and for her brother in what to expect with others..... but suggesting to him to change his computer to air when he is on nitrox is just plain wrong. a mistake. no one should take that advice.

 

[Diving Dubai]

change his computer to air when he is on nitrox is just plain wrong. a mistake. no one should take that advice.

Errr I do sometimes. (I always dive Nitrox) If I'm guiding and my divers have Air, I'll set my comp to air, and my conservatism values to match their computers, so I can more easily monitor their NDL.

Diving Nitrox but on Air "tables" just adds a greater level of conservatism as long as you respect and know the MOD of your back gas

If I'm teaching that weekend too so lots of dives between different groups of students, I will have 1 computer set to my gas choice to monitor my overall N2 loadings, but dive to a computer that matches their settings and gas

 

[Graeme Fraser]

If you are diving nitrox please do not ever set your computer to air thats just wrong. Second point his sister has and had over 700 dives.

SEVEN HUNDRED DIVES

No one needs to babysit a diver with that many dives who also surfaces with the most air every dive. she probably surfaced with the most air on this dive too..... she just did not understand the deco obligation....would she have died at any point? no . was it a very interesting story and one that will educate people? yes. did the brother need to change anything or do anything different? No.

Basically his sister kind of I wont say panicked but she freaked out over her computer.

Was his sister out of control or a danger to herself or others? No.

was she panicked in the real diver definition? no not by a long shot and not with her 700 dives and just her computer giving her info.

was she freaked out about it? oh yea and thus did her best to get to the surface.

its a learning experience for her and for her brother in what to expect with others..... but suggesting to him to change his computer to air when he is on nitrox is just plain wrong. a mistake. no one should take that advice.

Nothing wrong with diving nitrox and setting the comp for air as long as you monitor MoD. Only thing is the comp won't accurately track CNS and OTU, which is less of an issue in recreational diving.

 

[zixzax]

Yesterday afternoon my sister and I dived the Rebel wreck in Fort Lauderdale. The wreck is 128' long in about 110' to the sand. It's largely broken up but the bow and stern still have large open areas that can be penetrated. Because of her schedule my sister could not join me this past week of diving in South Florida but due to a last minute change she was able to join me for 4 dives on Sunday.

American Dream Charters has no "store", their shop is basically the back of a box truck approximately 20' long that sits on the parking lot next to the boat. Which is rather convenient by the way, as long as you don't need to purchase any dive gear. All their rental equipment is inside the big box including a compressor and dozens of tanks, and the boat is right there, they check you in at the boat and you can park nearby.

Probably because of their rather limited facilities, they don't have Nitrox available. Knowing this in advance, I had rented 2 steel 100 tanks from Gold Coast Scuba, with EAN 35 for this dive. I use a P02 setting of 1.6 for all dives but I'm getting off topic. Point being, since my sister joined me last minute, she was unable to get Nitrox so she was diving an AL80 on air. She's got an extremely low SAC rate, always surfacing with more than a half a tank while the rest of us are at our reserve. My sister is an intelligent woman but when it comes to diving, although she's smooth in the water and has over 700 dives, it's scary what she doesn't know about decompression.

We're about a half hour into this deep wreck dive and I've still got about 10 minutes left. I signal to her "is it ok" if I go and check out this forward hold one more time, she glances at her gauges, shrugs an "ok" so in I go, she follows and here I am pointing out 4 huge lionfish when she suddenly bolts for the line and starts ascending like she was about to miss a train.

I catch up to her on the line at 15' and she's totally freaked out- very unlike her. Gesturing, eyes wide, looking all around and pointing to her computer which says DECO, with an up arrow and "10''" and "1 minute". She's stopped at about 15' and has no clue. I calm her down with reassuring signals and gesture she follow me up to 10' but of course that's the last thing she wants to do. Luckily she trusts me when it comes to all things diving and gear related (although possibly not so much after this dive). We get to 10' and the DECO obligation is gone almost immediately.

We did a nice long 5 minute (or longer) safety stop until those dots got to the bottom of the yellow and the whites of her eyes looked normal again, and slowly ascended to the surface, with no issues.

Interestingly- and I messaged @scubadada about this- her Veo200 did not provide safety stop information. Once the DECO obligation was satisfied it simply reverted back to normal dive mode.

A few take-aways:

1- Know your dive computer! Especially what the alternate "DECO" screens mean. She had NO clue.
2- Watch your bottom time- She said "I just watch the dots go up the side and suddenly it went from yellow to DECO!" [nitrogen bar loading graph]. She didn't even monitor the "dive time remaining" numbers!
3- I suppose I bear some responsibility for going back into that hold, knowing I was on EAN35 and she was on air- but again- she's supposed to know her computer and after 700 dives you'd think she'd know if there was sufficient dive time remaining.
4- If she had panicked and surfaced rapidly things could have gone from "mildly bad" to much worse.

She's fine by the way and now she gets to tell everyone who wants to listen that she "went into DECO!".

And yes we sat down with the computer manual and went through all the different DECO screens and I showed her how you need to watch those big "DIVE TIME REMAINING" numbers right there on the face of the computer.

Thanks for sharing. I am a bit astonished that a diver with 700 dives have never had a deco experience. But I think you did well in calming her down.

 

[Zef]

SEVEN HUNDRED DIVES.

700 dives, or 1 dive 700 times?

-Z

 

[caruso]

FWIW, I calculate my MODs at 1.6, but I dont understand your point that seems to suggest no risk for diving EAN <40% past their MOD.

Little to no risk as long as you don't exceed P02 1.6. You can briefly exceed an MOD for a particular EAN mix and still be at or below P02 1.6, it's a matter of how long you do it.

700 dives, or 1 dive 700 times? -Z

Her diving skills are spectacular, she barely moves in the water and uses very little air, but her ignorance regarding some of the most basic aspects of diving is astonishing and I've spoken to her about it. She simply doesn't care. She only got Nitrox certified at my urging within the past year or so prior to another trip we did.

She said something like "What do I need that for, my gas consumption is great!". I just shook my head

If you were going to dive with your sister as a buddy, then you should have set your computer to air OR very carefully monitored her deco status on a 110 ft dive. After 30 minutes, if you had any sense of diving, you would know that she would be in deco or close to it. This is a significant diving error in my book.

No doubt. I completely left it up to her to monitor her bottom time and she was well aware I was on Nitrox and she was on air. But I'm also aware she's very ignorant and I should have been more on top of things, I completely own that and if she was hurt I'd have to live with that.

In addition, I would not have done what you did with your sister on the ascent. The OP indicates she took off and presumably started to ascend rapidly. In that situation and finding her at 15 feet with a 10 foot ceiling, I would have confirmed adequate gas supply and then I would have her descend to 20 feet or, at least stay at 15.

We cleared the DECO at 10 feet almost immediately, then dropped back to 15' and stayed there for about 5 minutes until the computer load graph was out of the red and into the yellow.

This is really a pretty significant lack of awareness of basic diving protocols. If you are going to do a deeper dive with someone who has the capacity to go way into deco (due to exceptionally low gas usage) and the two divers are using vastly different mixes - you gotta be looking at her computer during the dive.

If this scenario ever happens again you can bet I will be doing just that. Although I think she's got it now.

Thanks

 

[caruso]

Do you guys diving to 100' plus depths routinely plan those dives? Gas planning, buddy briefs etc.

We get together once or twice per year (more in the past couple of years) I'm in NY, she's in Florida. She only got Nitrox certified at my urging recently (and constantly complained about how it was a waste of money) but this time due to the last minute scheduling on her part she couldn't get Nitrox. This never happened before, but yes we do deep wrecks on most of our dive trips.

She routinely gets back on the boat and announces loudly that "she has so much more gas left than everyone else and she could have stayed down an hour!". Last year after doing a triple wreck trek with Ocean Divers she said the same after the second dive on the Bibb, and the captain said "You probably had another 2 or 3 minutes max before you reached your NDL limits". I said to the Captain "I've tried to explain this to her several times she just doesn't get it". She's got a half a tank of gas, that's all that matters. That Nitrogen loading bar graph is sort of a secondary thing that she barely glances at. But probably not any more.

 

[caruso]

No one needs to babysit a diver with that many dives who also surfaces with the most air every dive. she probably surfaced with the most air on this dive too.

I know how ignorant she is. I should have been more on top of things given the different gas mixes we were diving. She surfaced up with 700 psi I had 400 and I was on a steel 100 while she had an AL80. Edited- after looking at my uploaded dive profile I had a bit more gas than that, she and I were almost even.

but suggesting to him to change his computer to air when he is on nitrox is just plain wrong. a mistake. no one should take that advice.

I would never do that. A boat captain once suggested doing that as it was "more conservative". I just shook my head.

 

[Dan]

She said something like "What do I need that for, my gas consumption is great!". I just shook my head

I guess now she understands why after what happened.