"Accidental" Deco

[TSandM]

I agree that it's easy to come out of your OW class with the idea that, if you end up in deco, you are going to die In fact, if you think about it, technical divers go into deco all the time, and although the risk of DCS is somewhat higher when you are doing those dives, the vast majority of them still go without incident at all.

What is DIFFERENT about going into deco, and the reasons why recreational divers are taught not to do it, is that once you have a decompression obligation, you are truly obligated -- to remain in the water until you have cleared it. This means you now have to solve any problems that arise while you are underwater; the surface is no longer a good option for you. It also means you have to have enough gas to stay in the water until that obligation is cleared. One of the big things in learning technical diving is learning to calculate how much gas you will need for the dive you propose, because not having enough to do the deco you need is a very bad thing. And not only do you have to have enough gas to do YOUR deco, but what if your buddy has a problem, and loses his?

Decompression obligations add a whole big level of complexity to diving and dive planning, which is why recreational divers should take care to make sure they stay where they can always surface if it is necessary.

 

[RTee]

Wow, that's surprising. Most basic divers don't have the gas to maintain a proper reserve and get into that sort of deco. What tanks were they diving? Were they day diving or was it a series of repetitve dives over multiple days? Were they diving Suuntos?

Hey Hey...careful now...lol. I dive Suunto for both air and nitrox and I never got an accidental 10 or 16 mins safety stop. The only time it added an additional minute to a safety stop was a short burst exceeding 10 m per min rate of ascent. I have done deep and long dive and always maintained proper SA to multi-level my dive in order to remain on the NDL side. Unless you get snagged or decide to help somebody else experiencing a problem, you have very little excuse for busting your NDL.

Perhaps one thing to consider (if their dive time and profile was as per the other divers) is their dive computer personal settings...I dive P0 A0. If somebody decides to dive P1 or P2 due to some physical and or medical conditions then for sure their NDL will end up being shorter than mine even though we entered the water at the same time and maintain the very same dive profile.

 

[scubadobadoo]

What he said. Relax and take a deep breath. Your basic attitude is great - that divers should stay within their limits - but with time and experience, you may find that stuff that sounds extremely dangerous and/or reckless at first can be less dramatic when encountered in reality with some experience.

For example, i was once on a deep dive (135 feet max) with a friend who was an advanced diver with moderate experience. We were following down a line at a submerged dam in a lake. Due to the lake's plankton levels, it was completely dark at depth and we used our lights to keep track of things. Suddenly he shot up like a missile. I went after him, but decided to let him go as he was going up the line, and saw his light dangling back and forth and getting dimmer as he went up.

My other buddy and I started to ascend ourselves, but slowly. Back on the boat, we asked our third buddy what happened. He replied, I looked at my computer and discovered that I had only one minute of NDL left. That freaked me out.

With a bit more experience and perhaps a couple or so times of "accidentally going into deco" he would have known that racking up a deco obligation of a few minutes will a) most likely clear during a nice and slow ascent and safety stop, and b) put you in deco for a short time at 3 meters at most. Instead, he risked a rapid ascent injury because he did not know what to expect.

I agree and forgive me if I sound high and mighty (not my intentions honestly) but given that we are in the basic forum I would still say that proper dive planning would have been an even better option for your third buddy. The lack of it caused him to panic and that was with a whole minute left. I would hate to see how your friend might react if he did accidentally go into deco. His ascent may have been even more dramatic. Glad it wasn't though.

 

[Dr Wu]

I agree with Bubbletrouble. I attach a discussion of the issue that is quoted from my book, co-written with my wife Debbie, "The Scuba Snobs' Guide to Diving Etiquette" available on amazon.com or barnesandnoble.com in paperback or as an e-book.

LOOK AT YOUR GAUGES REGULARLY

Ok divers, listen up......... Live to dive another day.

This is satire, correct?

 

[DevonDiver]

As an instructor, I believe that divers should understand how to conduct emergency decompression. On the other hand, I believe that some divers have a natural inclination to want to 'push the boundaries' and providing information about basic decompression procedures is likely to give the false impression that conducting decompression is an easy task ("it's just a long safety stop" mentality) and will be taken lightly... thus encouraging those divers into scenarios that can easily prove to be beyond their capacity to deal with.

Having no information is a bad thing, and can leave divers unprepared.

Conversely, a little knowledge can be a very bad thing.

Entry-level divers are given basic instructions on how to complete emergency decompression. Whilst it is essentially a prolonged safety stop, there are significant health risk associated with any failure to conduct that stop at a precise depth for the prescribed time. As any decompression qualified diver will testify, the minimum standards of skill, equipment and planning necessary to conduct safe and assured decompression are well beyond the simple mechanics of doing 'long safety stops'.

Having a mindset that deco is nothing more than a 'long safety stop', or that small amounts of deco obligation will naturally clear upon ascent is very misguided. Whether deco clears, or increases, on ascent is dictated by the tissue compartments controlling the dive. It is unsafe to assume that deco will clear on ascent, without first having an awareness of how that deco is being calculated by the dive computer. The diver needs to understand how their prior dives are contibuting to that deco obligation and how their dive computer is likely to respond, based not only on the present dive... but also on the cumulative nitrogen absorbtion and retention from previous dives.

Unless a diver can hold an informed discussion about how tissue compartments and half-times contribute to the formulation of decompression in their dive computer, then they should not be making any assumptions about how their dive computer is likely to respond to overstaying an NDL on any given dive.

Having a few brushes with light deco situations, and then assuming that you understand and can predict your dive computer is a very naive and potentially dangerous mistake to make. Sadly, it is a mistake I have witnessed many recreational divers make.

 

[Hatul]

2 weeks ago one, of my infrequent buddies went into deco without knowing it. I only found out this past Saturday that he had bent his computer the previous week. I did not get to review his computer's log Saturday because his service called before we docked. One of his surgery patients was having problems with his sutures.

In any event, 2 weeks ago, Buddy was making his first dives in more than a year. He did not have his Eanx card, so he was only able to rent air. He normally dives single al 80's with ~36%. On a two tank trip, volume of gas is usually the limiting factor, not NDL's.

I thumbed the second dive of the day on that trip because of a mask problem. Buddy had a brain fart on that dive. Hooked up with another friend using 36% and simply over stayed, not recognizing RBT changed to deco.

He is fine, but did bend his computer. I have yet to check the log.

That's more than going into deco. To lock out his computer he must have ignored the deco stop and surfaced without stopping. There's nothing wrong with going to short deco for a rec diver, but it's a big problem to skip a deco stop. He was lucky only his computer got bent.

Adam

 

[DevonDiver]

2 weeks ago one, of my infrequent buddies went into deco without knowing it... Buddy had a brain fart on that dive. Hooked up with another friend using 36% and simply over stayed, not recognizing RBT changed to deco. He is fine, but did bend his computer.

I would define that as more than a 'brain fart'. To get into that situation would require a complete absense of gauge monitoring, a complete absense of dive planning, a complete absense of situational awareness....

Serious health impacts were avoided by luck, not judgement.

It's a pretty serious series of mistakes by the diver concerned. I hope it served as an equally serious wake-up call for him. Complacency must have reached a very serious level, to have permitted the basic skills, drills and procedures to be neglected to such an extent.

I think most divers experience a 'wake up call' occasionally through their development. The lucky ones get to learn the lesson without damaging their health... but there are always a few unlucky ones. Guard against complacency, because none of us are beyond making mistakes... and some mistakes we don't get away with.

My point is that unintentional deco should be seen as a grave mistake. Not because of the consequences, but because of the chain of errors that must be made to arrive at that result. It shouldn't be dismissed light-heartedly, neither should it be blown out of all proportion ("you're gonna die!"). Lessons should be learned though....it doesn't mean you are necessarily a 'bad' diver... but at the least, it should be an illustration that your core diving capacities aren't at the level you may assume them to be... and/or that complacency has reached serious levels.

 

[Mr Carcharodon]

As an instructor, I believe that divers should understand how to conduct emergency decompression. .

That rather begs the question about how they should do that. I'd offer a ratio deco approach but what is your approach?

A.

 

[eelnoraa]

what is the approach? what is the approach? I really want to know. I will look up ratio deco just to understand it in case if I need it. I don't plan to do deco dive. In fact, recreation dive (<=100ft)with GUE min gas requirement and EAN32, one would never go into deco with a single tank setup.

But I still want to know what is the approach for "accidently deco".

 

[Centrals]

But I still want to know what is the approach for "accidently deco".

I am talking about computer dive.
I never had more than 5mins of "accidental deco".
I would ascent slowly to 12m and stay for 1min, 9m for 2mins and clear the computer at 6m. Finally, surface at a rate of 1m per min. 3 hrs surface interval before next dive.