Going into decompression

Personally I am not that keen using computers,whether multi gas or not, in deco diving. They are far too unpredictable in what stops they give you during the dive, stops seem to be added on a completely baffling algorithm that Hawkings would be hard pushed to explain (yeah, I know it is ascent rate, temp related etc but still very unpredictable) . It may be a bit more inconvenient but tables can be relied on. If you cut a table on the surface then the deco stays the same underwater if you stick to the times and makes gas planning etc easier.
Even with a multi gas computer you need to cut all the tables anyway for all the options and who would rely on only one computer?

[Noel Johnson]

Steve, just a short note:

A computer will NOT give you more bottom time all it does is cut a custom dive table for the dive that it is currently doing. You can do saw tooth profiles if you want and it will still crunch the numbers and give you a no deco time because all computers are based on a decompression model. However you (the diver) will probably not feel too good afterwards and may need a little ride to a chamber.

I'm not having a go - far from it in fact - I'm just trying to convey the problem with relying on what is essentially a wrist mounted calculator. From what I've seen the Gekko is a good piece of kit (I personally use a Vyper which is similar) but it is important to note that they are not designed for decompression diving on more than one mix of gas.

Please, for god's sake, don't rely on it plan the dive first using the appropriate tables or the wheel and take a timer (watch, dtimer, whatever) which is set to zero when you start the dive just in case the computer goes tits up, which they can. This way you can keep track of depth and time.

Okay well it wasn't that short but I hope this helps,

Noel

[torbaydiver]

Okay thanks Noel  

[Noel Johnson]

You're more than welcome

[Stu Sheridan]

Originally Posted by [b

Quote[/b] (Nick Bown @ April 21 2004,13:43)]Personally I wouldn't say there is much point in doing deco unless its accellerated. Why hang about getting cold when you could switch gas and get out of the water in almost half the time and feeling far less tired?

<font color='#0000FF'>Hi nick, I think one thing to point out is that most divers work up to accelerated deco by getting bored with air deco!
We all do a fair bit of it as we progress thru our &quot;Dive Lives&quot;.

Aside from that, I did 29 mins between 12 and 6m on Backgas (21 %) doing stops after the Zen. It was glorious mate, I almost got sunburnt &nbsp;

Stu.

[Jen S]

<font color='#8D38C9'>

Originally Posted by [b

Quote[/b] ]Personally I wouldn't say there is much point in doing deco unless its accellerated. Why hang about getting cold when you could switch gas and get out of the water in almost half the time and feeling far less tired?

What about the added safety margin?!! A lot of divers I know(myself included) do switch gas for deco (usually 50%), but still do the stops that would be required if we were still breathing 21%. Ok, you are in the water longer, but you do feel far less tired and there is an added safety margin. There have been so many incidents of DCI just lately where people have stuck to the tables/ computer and still got bent, not only on deco dives but shallow ones too!

This is how the BSAC Advanced Nitrox course is taught. It's not until you do the Extended Range course you move into accelerated deco.

I also take tables &amp; a D Timer with me when I dive to double check my computer &amp; act as a back-up. I usually compare the two at the first deco stop, just be sure. I will say though, there has been occasions where the tables have given me less deco than the computer, so don't always think a computer will give you less deco!!

I will admit, I am keen to go the acclerated deco route when I get the chance. I currently have a Vytec and have on occasions used the switch mix facility and it has cut the deco time. However, the buddies who I dive with don't have this, so I have to stay down for the duration of their air deco anyway. I do often think though about the possible dangers of accelerated deco, seeing as many divers are getting bent just doing &quot;normal&quot; stops (or no stops at all) as I mentioned above.

Jen

[Fathoms Down]

Originally Posted by [b

Quote[/b] (Jen S @ April 22 2004,08:49)]

What about the added safety margin?!! A lot of divers I know(myself included) do switch gas for deco (usually 50%), but still do the stops that would be required if we were still breathing 21%. Ok, you are in the water longer, but you do feel far less tired and there is an added safety margin. There have been so many incidents of DCI just lately where people have stuck to the tables/ computer and still got bent, not only on deco dives but shallow ones too!

Hi Jen,

I was counting using any gas over basic Nitrox (40%) as accellerated deco, to the type of stops you are describing is accellerated. I'm not a big believer in using a rich(ish) mix for deco whilst following an air deco schedule as it means that you need to spend more time in the water which means your body temperature can drop lower than it needs to. I'm sure someone has done a medical study as to which is safer though! I tend to do my first stops on my back gas and then go on to an 80% mix and use an increased safety margin cut in to the tables. It works for me and the people I dive with but everyone is different.

Knowing the risks and assessing them is part of the deco training courses and why I'd recommend them to anyone considering deco.