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

[Diving Dubai]

if you have never been in deco, you have no idea what the computer will show or do

Without being flippant nor condescending, it will be shown in the manual.

Here is a link to the Cressi Giotto Manual I don't own one nor have I ever dived one (and chose it at random). I could look up it up online, and see from the index that page 15 gives a detailed description of what the computer displays and how it will react.

While a computer will guide you it can't help you if you've not got enough gas - so before going anywhere close to the NDL limits you should be able to figure out your gas time to surface based on yoru consumption rates

 

[caruso]

Many will say follow your computer but if you have no idea what your computer will do or show, then what? There is a chicken and egg here, if you have never been in deco, you have no idea what the computer will show or do. How do you learn this?

The Oceanic manual clearly shows and explains the alternate DECO screens.

 

[Manatee Diver]

The green appears and goes away if I toggle "calculated ceiling" which would support what you said about me potentially being in DECO but again it never happened during the dive. Go figure.

Ok, if I were to guess, it is what your deco status would be if you were running a proper Buhlmann algorithm at 30/75 (which is pretty conservative, I run the medium setting on my Teric which is 45/85).

 

[caruso]

My sister now has a bumpy itchy rash on the back of her upper thighs. I'm thinking skin bends (more from her rapid ascent which was steeper than the one in my profile). At my urging she called DAN who told her it's probably nothing to worry about.

 

[Charred]

Without being flippant nor condescending, it will be shown in the manual.

Here is a link to the Cressi Giotto Manual I don't own one nor have I ever dived one (and chose it at random). I could look up it up online, and see from the index that page 15 gives a detailed description of what the computer displays and how it will react.

While a computer will guide you it can't help you if you've not got enough gas - so before going anywhere close to the NDL limits you should be able to figure out your gas time to surface based on yoru consumption rates

Well, don't shoot the messenger... *I* know what my screen looks like.

Lots of people getting locked out of computers which means they don't understand this. Do you tell them to RTFM? Is this really the solution?

Buy a computer, read manual, 3 years later they stay 1 min too long....now what?

Why does training require demonstrated proficiency in so many skills far rarer than someone overstaying NDL by 1 min?

 

[Storker]

Why does training require demonstrated proficiency in so many skills far rarer than someone overstaying NDL by 1 min?

Deco: measure with a micrometer, mark with a chalk, cut with an axe. But you have to draw a line somewhere. Even if it's a hard black line drawn through a fuzzy gray continuum. I really prefer to stick with recommended limits, just to have a hard limit that I don't exceed.

Read up on "slippery slope". And "normalization of deviance".

 

[Dan]

I like to take underwater pictures. To manage task during diving, I just monitor 3 parameters once in a while. Those are pressure, depth and time. Pressure is normally not the limiting factor with my 0.4 cfm air consumption. So does with my buddy who has been diving 30+ years and logging 1000+ dives. Our limiting factor is NDL diving time.

My dive computer time display would normally show No-Decompression Time (how much time remaining I have at that depth). Normally that time will go down during diving. If I get distracted and get into deco, that time would would start to go up, instead. That time simply means that I’m in deco obligation time and my bottom time is up. If I stay at that depth, I’ll accumulate more deco obligation time and it’s time to ascend. So, I’d calmly give my buddy a thumb up signal and point to my dive computer. We just start to ascend normally and watch the deco obligation time going back down to zero. We usually don’t exceed NDL by much, may be 5 minutes at the most. By the time we reach safety stop, it would be cleared and start counting down 3 minute safety stop.

 

[luscioman]

I'll add this addendum to my post on the first page.

I dive a CCR, and have done for a long time now. Most of my buddies are OC.
I wear an OC computer on my right wrist. This allows me to track my buddies deco' obligations. I can switch gases, on it and accelerate the decompression if I wish. By default I set it to air, if my buddy is using Nitrox, i reset the computer before the dive to match.

Having my OC computer gives me an indication of my buddies decompression obligation. At 4 or 5 minutes NST remaining, I will check with my buddy how he/she stands.

An additional note. If you are using a different computer to your buddy, even a different model from the same manufacturer, there is no guarantee that you will have the same NST time, or the same decompression data. (Obviously if either of you has done a dive prior to buddying up then one of you will have a residual nitrogen loading.)

When I am guiding I always set one of my computers to be conservative and to whatever mix they are on. This is usually AIR so I roughly aware of where they are at in regards to deco.

 

[Diving Dubai]

Well, don't shoot the messenger... *I* know what my screen looks like.

Lots of people getting locked out of computers which means they don't understand this. Do you tell them to RTFM? Is this really the solution?

Buy a computer, read manual, 3 years later they stay 1 min too long....now what?

Why does training require demonstrated proficiency in so many skills far rarer than someone overstaying NDL by 1 min?

The reason computers lock you out, is to punish stupidity or negligence. You get locked out for missing your stops - so yup I say RTFM.

If you miss stops through a real emergency then sitting on the beach for 48 hrs to take a rest is not a bad thing.

The next solution is for them to get training, not just in theory but in practical skills too. As I said earlier I'd make that a compulsory step either included (Using PADI Parlance) within Rescue or as another step prior to MSD or DM.

Once you have the knowledge and training you can make informed decisions - until that you don't' know what you don't know.

I encourage people to take Tec 40 because even if you never wish to go into deco (10mins max) the training knowledge and techniques are absolutely applicable to Rec diving

 

[Edward3c]

Two things:

1. Not all CMAS 3* require deco, PADI DM doesn’t.
2. Commercial agencies like PADI/SSI don’t want to teach anything that can be taught in another income stream. Deco is an income stream for their technical courses.