Would you really know what was going on if your computer went into Deco...?

[diverbrian]

I see at least four issues with that plan:

First, What do you do when your computer floods or otherwise fails after you've incurred a significant deco obligation, i.e., a 30 minute hang with one or two gas switches.

Second, does your computer have a simulator that will calculate the amount of gas that you'll be using? If not, how do you determine whether you'll have enough gas to complete the dive safely.

Third, with certain limited exceptions, most computers can't handle mixed gas diving. Assuming that you've got one that does, it won't matter when it floods or fails unless you've got a fully redundant backup and you've been adjusting both for your gas switches.

Fourth, if I'm going to go through the effort to plan a dive, I want to know that I'm going to have enough gas to reach my objectives. I don't want to wait until I get there to find out that I'm not going to reach my objective because I didn't take enough gas.

Your analogy to computers on planes is interesting and accurate. Just like when your diving, people on airplanes get hurt or die when the computer screws up.

I have my gas use planned for both deco on EAN50 and Backgas if the my mixed gas computer is unavailable. My back-up dive computer is my Cobra so it is more than capable of handling deco on backgas. Oh, once it clears, I still hang out at 10-15 ft. under the boat waiting for everybody to come up.

In short, I use the gas management tables provided by IANTD (or Voyager software) to make sure that the dive I want is possible before I start. I keep this info on my wet-notes for an emergency. Then, I let the dive computer do it's job and keep track of my nitrogen loading. Then I don't have to worry about going to this PITA process for an NDL/multi-level dive later in the day.

I have done enough of this now that like my dive buddies, I have my IANTD tables for my max allowable deco pretty much memorized (20 minutes at 130 ft. 1 min./20ft. 6 min./15 ft. for EAN50 and 8 min./15ft. for backgas off the top of my head.) I pretty much just turn the dive at 11 minutes and head back anyways.

 

[IndigoBlue]

Would you really know what to do...?

Have you ever done it...?

I wonder if it might be a good idea to intentionally run it over a couple of minutes in the red in very calm and controlled conditions then work off the Deco obligation plus 3-5 minute Safety Stop as well - all as a practice & learning session?

I've asked a few, and the most common response is: "If it beeps, I'll know I have a problem to ask about." :klo:

don

If you have a DIVE SIMULATION mode in your computer, like the Suuntos do, then you can play this game while sitting on your couch at home.

We do not teach divers to intentionally go into deco just to practice with their computers. We teach them to avoide the limits of the NDLs. You would be violating this teaching principle if you played with the deco mode of your computer underwater.

If you want to learn about deco, you should take a STAGE DECOMPRESSION class. IANTD, TDI, NAUI, GUE, and ANDI all teach these classes.

You should never toy with trying to do something that you have not been trained to do, because it could get you killed in scuba diving.

 

[IndigoBlue]

...

There is a lot more to doing deco stops than just staying in the water longer. If you have not been trained and do not know how to plan your dive properly, then stay within the NDL.

Absolutely right.

 

[matt_unique]

I foolishly used my Suunto computer for short deco dives before I was trained in deco diving. I learned on the first day of class that there are perhaps one or two computers available that provide reasonably accurate deco information. I thought if I fulfilled the deco obligations on my computer I would be fine. My instructor provided an example of a DM who used two computers for a deco dive to 130'. He cleared both computers (of varying conservatism), added a 3 min safety stop, and still got bent. He made the same mistake and incorrect assumptions about using recreational computers for deco diving purposes. Now of course we all know there are many variables that can lead to an injury but the point is not to reply on computers for deco diving.

The norm is to use software such as from GUE or V-Planner to get a schedule of stops. The GUE software tends to add one stop deeper than the V-Planner but from my research both are used by a lot of deco divers. You then take these profiles with you on a slate and use your computer only as a depth gauge and timing device.

After my class I plugged the details of my 'before training' deco dives into this software and was dismayed to learn what I should have done compared to what my computer required me to do at 10 feet.....

--Matt

 

[rcohn]

A reasonably safe way to practice short deco times is to use an appropriate nitrox fill while running your computer in air mode. This way you can run up several minutes of deco time on the computer while remaining within safe NDLs. You should use tables or a second computer to confirm your profile is safe.

This is more useful than simulation mode because you will see how the computer reads under real conditions and how well you can control your profile needed to clear the deco obligation.

This is no substitute for proper training in decompression techniques. However, completely understanding your computer so that you will know how it reacts and what you should do if an unplanned deco situation occurs is valuable.

Ralph

 

[ChrisF]

A reasonably safe way to practice short deco times is to use an appropriate nitrox fill while running your computer in air mode. This way you can run up several minutes of deco time on the computer while remaining within safe NDLs. You should use tables or a second computer to confirm your profile is safe.

This is more useful than simulation mode because you will see how the computer reads under real conditions and how well you can control your profile needed to clear the deco obligation.

This is no substitute for proper training in decompression techniques. However, completely understanding your computer so that you will know how it reacts and what you should do if an unplanned deco situation occurs is valuable.

Ralph

Exactly! I see nothing wrong with this approach.

 

[Genesis]

There is no specific need for "training" in decompression.

However, if you're going to do mandatory-decompression dives, you had better understand how decompression works! After all, its YOUR body you'll be screwing up if you don't!

 

[truva]

Deal with it like any other issue that comes up, if it isn’t OOA, you don’t have a problem.

Hmmm. I’d use a little bit of common sense, and remember we are talking about a small amount of deco obligation here like 15 minutes or so. Since I use an AI I would be out an SPG too, now in 10 years and over 1200 dives I have yet to see one of these flood, I would make the informed decision depending on the dive profile (non (hard) overhead) to go over and dive off my wife’s computer instead of ending the dive. See I know they are ultra conservative (like me) and we’d go up sooner and maybe hangout at until I was near to OOA.

All dives are deco dives; I see nothing wrong with entering into one that has a ceiling because I just wanted to stay down there a little longer just be sure to use common sense.

Truva

 

[NEWreckDiver]

There is no specific need for "training" in decompression.

However, if you're going to do mandatory-decompression dives, you had better understand how decompression works! After all, its YOUR body you'll be screwing up if you don't!

If you don't need specific training for decompression dives, where would you learn?

 

[Genesis]

There are multiple ways to learn something - buying training is not the only way, and it may not even be the most effective method.

One of the reasons for this is that by definition if you are buying training you don't know enough about the subject to evaluate the prowess of your would-be-instructor. Thus, you are always doing what amounts to a "trust me" - and when it comes to things like decompression, you are betting your life (or at least a significant amount of pain and expense) that you're right in your evaluation.

The necessary understanding of the physiology, procedures, etc out there to do decompression diving is quite attainable without playing "trust me."