Uncontrolled free ascent

[b1gcountry]

Ts, I dont really agree with what your saying here at all. There is a reason that the no deco limits are pounded into the heads of OW divers, while deco is purposely only lightly described. A new diver has literally dozens of things to worry about, the thought of even approaching the nodeco limits, let alone actually having to worry about making a deco stop should not even begin to cross their mind. telling a new diver that they will most likely be fine if they just relax and make the deco stops, and that "you don't turn into a pumpkin because you exceeded your no-deco limits." is sending an entirely false and probably dangerous message to a new diver who has absolutely no experience. Getting caught in a decompression situation is the same as a pilot who accidentally wanders into instrument rated conditions, for someone whos been well trained in IFR it should be a walk in the park, but for a new pilot who can only fly using visual flight rules it often ends in a death sentence. A deco dive to you or I may just be another day in the water, for a rookie diver whos just getting the hang of buoyancy control, let alone tech diving skills, it can often leads to a nice long painful chamber ride.

Arrgh! No. The equivalent of this in flying is having the pilot fly into a instruments only situation, and then having them go into a nose-down dive because "being on the ground is safer". Being on the sufrace is not always safer than being in the water at any given moment.

No, I've read a lot of Lynne's posts, and she is not encouraging anyone to plan any mandatory decompression-stop dives without training. When the #@$% hits the fan, though, and your computer starts giving you deco obligation, you are sure as heck better following it than shooting to the surface. And just so everyone is on the same page, exceeding any of the NDLs on the PADI RDP by five minutes or less would give very minimal decompression obligation. If you do not have enough gas to spend 10 minutes at 15feet, then you did not have enough gas to start off with.

If you screwed up and overstayed your bottom time, that means you made a mistake, and you have to correct that. It is better to deal with a decompression stop, than to deal with DCI, or a fast ascent to the surface.

PS. Another thing I would like to point out is that even if you have reached your NDL at 120', you can still ascend and have bottom time left at 20' or less. A common misconception is that when your body is 'full' at depth, that spending any more time underwater at any depth makes it worse. It doesn't. If you ran out of bottom time at 120', you would have less nitrogen loading by slowing ascending to 40' and continuing the dive for 20 minutes than by shooting straight to the surface (I am not RECOMMENDING either, just stating a fact). If you don't understand this, do a search on Decompression Theory and Tissue Compartments.

 

[Jim Kerr]

I think this is the first post on this thread, but I thought I would post to help me get more recommendations help me understand how not to make this mistake again.

Here is some information of me. I am an new OW diver with less that 10 dives.

I was diving with a dive guide in Hawaii. Dive guide took us down to 126 ft during the dive. On the way, back up I became concerned about my bottom time after looking at my dive computer. It seemed to me that I was out of bottom time. I began to try to surfaced and I pressed the inflate button instead of the purge button (have a seaquest octo-inflator and the two buttons are very close together and easily mistaken). I was at about 45 ft and ended up on the surface in a few seconds. The dive guide had me go down again and take sometime diving and do my 3 min safety stop.

There are a couple of solutions to the problem that I have come up with or suggested by another dive guide on the boat. First, I need to ask what depth the guide is planning on taking me before the dive and indicate to him that I am not comfortable diving to that depth. Second, I am starting to use my dump valve on my right shoulder to empty air out of the bc before ascending and will doing my safety stop. Third is instead of ascending all the way, I should try ascending a few feet to buy more bottom time and more time to assess my situation.

Any other suggestions would be greatly appreciated.

Thanks,
Blake

You should always find out the approximate depth ranges of the dive sites a charter boat plans to visit. If it's a wreck dive then you know it will be deep. If it's beyond rec limits then it will be stated as such and they will make sure that you have the proper training before they even let you dive.

On sites that come close to the limits of rec diving some ops will require you to have an AOW cert and/or proof of recent deep dives beyond so many feet. (Keep in mind, an AOW card "DOES NOT" make you an advanced diver, only experience will do that).

Some ops (like the one you were with) will only require you be a certified diver and will take you to any depth within rec limits. So do your home work before stepping onto a boat and find out where they're going and what they require. Because "you" aren't comfortable with going beyond a certain depth doesn't mean they will change their itinerary. So if you're not comfortable with where they're going, find another boat that will go to sites you're comfortable with. It also helps if you're honest with them in the begining about your experience. If they know you only have a handful of dives under your belt they may be able to adjust their itinerary or schedule you for a different time.

If you are not familiar with your equipment don't try to do it on deep dives. There is too much to think about on deep dives and learning your equipment should not be one of them. Being concerned about how long you've been at depth should not come to you when you're on your way up but should be monitored during the "entire" dive. Depth, Air, NDL and BT should be monitored even closer on "deep" dives.

Something else to think about when going deep is getting "NARCED". It's possible that you were narced and became complacent when you were below 100 ft. When you became concerned with your BT probably occured when you ascended "above" 100 ft and the effects of being narced wore off.

Like was said earlier, simply ascending (slowly) to a shallower depth can increase your BT and NDL, and decrease and even eliminate any 'deco" obligation, depending on how bad they were violated.

Learn how "all" of your equip works and then go have some fun.

 

[hudson]

Getting caught in a decompression situation is the same as a pilot who accidentally wanders into instrument rated conditions,

Bad analogy. You can't really get yourself out of IFR conditions by sticking around for a little bit. If you accidentally get into deco, you can, there is no need to panic. The message is spot on.

The equivalent of this in flying is having the pilot fly into a instruments only situation, and then having them go into a nose-down dive because "being on the ground is safer".

Good one, but he was referring to the deco situation not the ascent

Any other analogies I missed? I could rate more while I'm still warmed up

 

[beester]

The third lesson is that you don't understand decompression and "no-deco" limits very well, and that's not entirely your fault. Decompression is taught at a very primitive level in OW classes. The fact is that, if you exceed your no-deco limits on your computer, you may be just fine, especially if you are using a conservative computer and it's your first dive of the day. Or you may not be fine, but if you DO the deco that you incur, you most likely will be. The big issue is if you have enough gas. But my point is that seeing the clock tick down on your computer is a reason to signal your buddies and indicate a desire to ascend, but it is NOT a reason to panic and shoot for the surface. My husband's computer got mad at him on a repetitive dive in LA, and we sat in ten feet of warm, clear water and played "rock, paper, scissors" until his computer was happy. You don't turn into a pumpkin because you exceeded your no-deco limits.

Of course, it's not something you WANT to do, or OUGHT to do, and you should have PLANNED the dive so you wouldn't do it. But divers are too afraid of decompression, and a poorly controlled ascent is much more dangerous than a few extra minutes at a safety stop (assuming you have enough gas to do the stop).

Bottom line -- Don't dive without a plan. Know the parameters of the dive -- depth, time, direction, and gas. Have an idea of what you'll do if something doesn't go as planned (contingencies). Don't entrust the safety of your dive to someone else, no matter what their title is.

Very well put...

You of course shouldn't have been there at that depth... specifically with buyancy issues. However as Sandy put... you mostly won't die from going through a couple of minutes of deco ceiling.

Your divecomputer is based on divetables with theoretical saturation models (going from haldane, us navy, buhlmann to the recent RGBM models) that have evolved from both trial and error and theoretical calculations. They will give you a black and white solution to a very grey problem.

How your body reacts to nitrogen saturation depends not only on who you are physically speaking (how old, fit, possible pfo,etc you are) but also on day to day variables (sick, tired, dehydrated, binch drinking the night before, etc). So there is no real border between no deco and deco... only a grey area (many will even say that every dive is a deco dive since you are saturating). All anybody can say is that the risk of deco ((micro)bubble forming) will increase the closer you get to your no-deco limit.

That said... your real danger during this dive was your uncontrolled ascend (blowup?) from 45 feet.

If you would have had pulmonary barotrauma or arterial gas embolism because of your blowup you would have been basically dead... unless professional help is administered straight away (and even then). Even a large case of DCS type 2 will have a better chance of recovery then the above injuries. During our OW-AOW courses our instructors stressed that the main risk of death for recreational divers is not DCS but barotrauma and AGE.

Anyway glad that you're ok and you've got one to notch up on experience.

Cheers

 

[schmal]

How did you know I was French?

 

[b1gcountry]

How did you know I was French?

Oh, I didn't. I was making a bad Monty Python joke since the original title of the post was uncontrolled free accent.

Cheers!
Tom