TDI Deco Gas Reserve

[aerobrain]

Can someone with access to a TDI Deco Procedures solve a discussion topic. What do they recommend for calculating Deco/Ascent gas? Is it double or 1.5(rule of thirds)

My manual is at home and we will soon be on the beer so need to solve before we get handbags out :-)

[kingfisher]

Can someone with access to a TDI Deco Procedures solve a discussion topic. What do they recommend for calculating Deco/Ascent gas? Is it double or 1.5(rule of thirds)

My manual is at home and we will soon be on the beer so need to solve before we get handbags out :-)

If you are diving as a pair, it is double.

Enough for you to complete your own deco requirements using your deco gas and enough for you to also give your deco gas to your buddy so he can complete the same deco requirements - i.e you both complete the deco times on the required gas (plus you will be using your back gas when your buddy is using your deco gas so you will both be adding conservatism.

[gobfish1]

I'm so happy I never bother with all this gas planning bollox

[JPTaylor]

...

[Mark Chase]

Buddy OC gas reserves on deco gas????

All fine and dandy till you get to 70m+ then it all goes to rat s#it

Its hard enough to carry your own gas needs

ATB

Mark

[Dammyla]

To be fair mark, by the time you are doing 70+M, you should know enough to make your own mind up

I was taught to go with x2 at the andp level but as most of the people I dive with are same ocean, same shot line buddies, I worry about myself first and them later

I stick to x2 ish for proper buddy diving

[The Duck]

Can someone with access to a TDI Deco Procedures solve a discussion topic. What do they recommend for calculating Deco/Ascent gas? Is it double or 1.5(rule of thirds) ...

At the risk of actually answering the question ...

My TDI Deco Procs book (2000) does not contain [any] recommendations for reserve gas.

In fact the only reconmendation for deco gas reserves is in "Extended Range Diving & Trimix" (2002), which is x1.5, thought this reads more of a recommendation and not a hard & fast rule.

In my old worked examples 1.5 was used.

[iamyourgasman]

On my ANDP and Trimix course we used 1.5x for deco gas planning.

[Woz]

Easier to work out the max deco you can do on the deco cylinder you own then plan dives that need less than this. Tada! One gas calc does all your planning forever. Well until you go diving stupidly deep with Chasey.

[Mark Chase]

I am assuming all these people who carry deco gas reserves for their buddy have deco stages with two regs on, preferably one a longer reg?

In the real world, you can easily loose back gas but it’s pretty hard to loose deco gas. That said there have been incidence such as Captain Deco who switched to his 50% to find it was 50% oil and un-breathable.

In such circumstances I have herd and\ read it said you should deco out on back gas????? What utter rubbish.

The safest course of action is to plan deco normally and then plan deco on a single gas option. IE if your carrying 32% and 80% you should be able to finish deco on either gas. The operational window for this strategy is very small. (do the deco numbers on 32% and you will see why) but it is a stop gap option from that to a drop tank

The most sensible course of action always being a drop tank and yellow bag protocol.


ATB

Mark