Deco without deco training

[ianr33]

Lots of good points in the above 2 posts.

I've done plenty of deco dives using an Aeris Atmos Pro (Oceanic/Pelagic computer )

Will use this for light deco dives,say, max 130 for 25 minutes. A profile such as that will probably only have a 10 foot ceiling indicated,but thats not what I do. Instead I'll come up to 70,slowly dawdle up to 30 feet over several minutes then up to 20 AND WAIT THERE UNTIL IT CLEARS DECO. After that will go to 10 and wait for it to get into the green before surfacing. This may well be more conservative than needed bit it works well on local dives where we are in no rush to get out of the water.

Have also noticed that if pushed too hard it can start suggesting garbage. e.g 2 hours deco when 30 minutes is more realistic. Getting that info as a recreational diver on a single tank would be interesting.

Disclaimer: I am deco trained and always have tables and backup bottom timer in case of computer failure or whatever.

 

[ucfdiver]

I agree with most everything that has been said, but would add this. Most people who stumble into a deco obligation are using computers that were never designed to handle a deco dive. In short they "punt" a solution and lock you out. Time and again I have witnessed the stumbler say " I do not know why my computer locked me out? I stayed at 10fsw for blank minutes like it said." Education is the key and gateway to safer diving, not simon says on my puter.
Eric

Add this to the list of why computers are a silly idea. I don't follow the latest and greatest, but it seems you can't read many threads on here without reading how a computer caused some weird issue on a dive.

I'm still doing 2-3 hour baby dives. When I do dives that "require" a computer (lulz), maybe I'll invest in one, until then it's just unneeded complication and something that always seems to evolve into a crutch...

 

[MXGratefulDiver]

Add this to the list of why computers are a silly idea. I don't follow the latest and greatest, but it seems you can't read many threads on here without reading how a computer caused some weird issue on a dive.

That doesn't make dive computers a silly idea ... it just makes using them improperly a silly idea. Dive computers are just another tool ... some people will use them properly, some improperly, and others not at all ... just like every other choice you can make in recreational equipment.

What's really a silly idea is rationalizing why your way is better than someone else's. Your way is appropriate for the way you dive ... nothing more. There's a lotta world outside those caves, yanno ...

I'm still doing 2-3 hour baby dives. When I do dives that "require" a computer (lulz), maybe I'll invest in one, until then it's just unneeded complication and something that always seems to evolve into a crutch...

I take it you've never used decoplanner?

Dive computers are nothing more than another algorithm-delivery mechanism ... at a fundamental level they're no different than tables, or even something like ratio deco. They don't "always" evolve into a crutch ... depends completely on the user. For the majority of divers, when used properly they are a very useful tool.

Stereotypes are a silly idea too ...

... Bob (Grateful Diver)

 

[Slamfire]

What most people read in the numbers amounts to something like "go to 10 feet and stay there for X minutes before surfacing".

That can get you bent if you follow the classic 30 feet per minute (or 60 feet per minute for some agencies) that you learned in your OW class. So you need to have a basic understanding of how an ascent affects your body once you've crammed it full of nitrogen, and "shape" your ascent accordingly.

You should begin your ascent at the recommended pace, make at least one (and preferably more than one) intermediate stop beginning at about half your deepest depth, and proceed to slow down as you go up. Deep divers tend to slow down to about 10 feet per minute, and make progressively longer intermediate stops as they get closer to the surface...

Let me take it a step further, and say that even staying within the NDL could still be putting the diver at higher risks than purposefully taking the computer into deco for a few more mins and doing a well structured ascent as you describe above. I'm not talking about major deco dives here. This is thinking about recreational diving with no massive amounts of gas or heavy cylinders.

Early on in my informal training I was taught panic will be my greatest enemy. When I'm underwater, my movements should be smooth (sometimes perceived as slow but not necessarily so), efficient, and purposeful. This is even more crucial when dealing with problems underwater -- particularly because you may find yourself with your lungs burning to take a breath when there may not be gas available at that instant. Better take your time and fix things to make gas available than to freak out and pass out.

The OW formal training I took made no mention whatsoever of panic and how to handle it. At the end of the course I privately questioned the instructor/lds owner about this apparent oversight and he told me that at the OW level they purposefully avoid mentioning panic because diving is now made safe with technology and better equipment. I also questioned him about why the tables that he just taught me had no mention or even hints about basic decompression, at least not to the level that I learned informally when using the USN tables.

Now with that in mind... :

Picture a hypothetical recreational diver in our local PNW/Western Canada conditions. He plans to dive on a Saturday morning at a site that's less than 30 mins away from home. Because he doesn't want risk peeing in his drysuit he doesn't drink water, and he's not used to having breakfast so he goes out on an empty stomach and not having had a drink of water since the night before. He goes to the site climbs down the steep cliff (Ansell Pt.?) to the water and drops down to slightly more than 100' on a shore wall dive.

He stays at depth until his computer shows that he's got zero mins of NDL, but still hasn't spit out a deco obligation. He then "rushes" at an ascent rate of slightly more than 30 ft/min all the way to fifteen because he is quasi panicking about the big bad NDL monster that's about to catch up with him. At fifteen he stops and relaxes for 3 mins and then just pops up on the surface at around 60 ft/min. After all he's heard somebody say that USN tables at some time had a 60 ft/min limit and he's so shallow that the water pressure must be really low.

He feels hungry, thirsty and dry mouthed, and wants to pee. So he starts the intense climb up the cliff immediately. After all he's got some beers in a cooler in the car that'll help with the slight headache that he assumes comes as a result of the Canadian Rye he had with some co-workers Friday after work.

I'd think that this hypothetical diver is a far better candidate for getting an "undeserved" hit than hypothetical diver #2 who, with no formal deco training, routinely takes his computer into ~5 mins of deco obligation BUT he does his ascents like Bob described above. After all, most, if not all, of the 5 mins will probably clear out while on the ascent. Hypothetical diver #2 would also wait at least 20 mins at the shore before engaging the cliff climbing. While climbing back, he would rest frequently to avoid exertion. He would also be well hydrated before and after the dive and would have avoided drinking alcohol the night before.​

So even though it would be easy to brand diver #2 as irresponsible for diving beyond the scope of his formal training when he takes his computer into deco, I think he'll have a better chance at not getting bent.

 

[NAM001]

I was reading my elite t3 manual. specifically the deco portions. I found out that deco stops displayed at most say stop >60 ft . if a deco stop is needed at 70 you dont see 70 ft for 3 min. I read this because i saw an article stating that recreational computers may show a deco 50 ft 10 min. with that statement you would think you should go to 50. in reality, per the article, you need a 10 min seco stop no shallower than 50 ft. so some at 70 and 60 is what you should do. Also after reading a bit about ratio deco i believe i can do the 70,60 ect per the ratio deco theory and probably the 50 ft will clear as mentioned by another poster. made me ask why do they not say >50 for 10 min. i am thinking that for 130 ft and shallower the ratio deco should work ok and never get the aformentioned deco 15ft 10 min.

The problem i see with my t3 elite is that the credit for the deco stop is not given unless there is a stop in a 10 ft window imediately below the displayed deco depth. 50-60 ft. not doing it adds required si time to off gas.

i will say that if you dont do it right the puter will show your ndl levels higher than what they are by virtue of time penalties ect.

i would welcome any opinions on this as i dont do planned deco dives. I am not afraid of a little unintentional exceeding of ndl either. burger and fries with a double SI is a great fix.

 

[Doc Intrepid]

The big challenge with recreational divers and "oops I screwed the pooch" deco is having the gas to do it. Divers who don't pay attention to their depth or bottom time generally don't pay much more attention to their gas, so about the time they realize they have a deco obligation they also realize their gas is getting low. Following George Irvine's observation that "we can fix bent, but we can't fix drowned", they'll tend to cut their deco short if facing insufficient backgas.

A "little unintentional exceeding of NDL" is one thing, and it will generally clear during the ascent and safety stop - but if a recreational diver frequently finds themselves decompressing on ascent, they need to stop and rethink their approach. One day they're going to run out of gas before the computer clears deco, with predictable results. If a recreational diver isn't pre-planning deco gas in their gas plan, they have no business doing deco. If they want to learn more about deco, as another poster suggested, download V-Planner and begin taking a look at what goes into doing it correctly.

 

[gcbryan]

I think, in a lot of cases, a little "unintentional" deco may just mean that they didn't necessarily plan for deco on that dive but they have thought things through to the point of knowing what their options are. Then if things are interesting at depth they just use one of those "pre-thought out" options.

If your local dives are roughly 120 fsw with a hard bottom and you know that sometimes on these dives while at depth you decide to stay another 5 minutes you've figured out that you need to roughly double your extended stay time as a deco margin as an example.

Obviously, many people "doing a little deco" end up posting about almost running out of air but in many other cases I think it has more thought to it than it may seem at first glance.

 

[NAM001]

The big challenge with recreational divers and "oops I screwed the pooch" deco is having the gas to do it. Divers who don't pay attention to their depth or bottom time generally don't pay much more attention to their gas, so about the time they realize they have a deco obligation they also realize their gas is getting low. Following George Irvine's observation that "we can fix bent, but we can't fix drowned", they'll tend to cut their deco short if facing insufficient backgas.

A "little unintentional exceeding of NDL" is one thing, and it will generally clear during the ascent and safety stop - but if a recreational diver frequently finds themselves decompressing on ascent, they need to stop and rethink their approach. One day they're going to run out of gas before the computer clears deco, with predictable results. If a recreational diver isn't pre-planning deco gas in their gas plan, they have no business doing deco. If they want to learn more about deco, as another poster suggested, download V-Planner and begin taking a look at what goes into doing it correctly.

i agree. the times i found my delf hitting deco was from repeditive dives. i dont recommend entering that relm to any one. only that it is not the end of the world. and using extended SI if not quiting for the day would usually clean things up. to push these type of things as "normal" is not the thing to do. i hope i did not offer that impression that untrained deco is ok.

 

[waterpirate]

As stated above it is "just a tool" how you choose to use it is up to you. By understanding your puter you will better understand where you "really are, in relation to nitrogen loading".
I said earlier that if your unit is not set up to handle deco it is just punting you out of the water, a simple default setting if you will. Most rec units are verrry conservative, but the owner needs to know how much so to be able to proccess the information it gives you in "real time-real world. All this takes effort while not diving and promotes the tennant of "the thinking diver".
I would suggest that the moment you become the thinking diver and get some mental input from somewhere you are no longer a stumbler and these questions will easily be resolved by your organic puter.

There is no substitute for:

dive planning
gas management
bail out planning
organic puter

As a side note I cut tables for every dive. I have puter a for another opinion. My choice of standard op. Some of my buddies dive thier puter and have cut tables for another opinion. It all boils down to organic puter choices, based on information and education. Darwin usually does not allow substitutions.
Eric

 

[FritzCat66]

You know, I often see references around here to the superiority of the "organic computer". And while of course generally speaking that's true, nevertheless between organic and digital, one of them is KNOWN to start having problems at depth due to narcosis, even before the diver is aware of the effect, while the other is immune.

So, the organic computer is not always supreme. You may think your organic computer is always correct - but then, think about it, who's whispering that in your ear?