Deco gas planning and risk mitigation.

[elan]

I'm just playing here with deco profiles and it would be interesting how would you plan this case.

Say you have a deco profile for which you have enough back gas + some safety margin amount. + you have one deco bottle with you which covers the deco. While the amount of back gas is enough for the bottom it is not sufficient to complete the deco in case you lose your deco bottle for any kind of reasons.

What would you prefer to do.
- reduce the profile so you can complete the deco on the back gas in case of deco lose
- sling a stage with the back gas
- count on the team to cover you

other


Thanks

 

[SailNaked]

I'm not trained yet so my opinion is worthless. for me Deco requires redundancy and as such i would limit my bottom time so I could accomplish my deco with the back gas if I lost my deco bottle, or I would have a redundant system for deco gas.

 

[BabyDuck]

well, you always have to plan for lost gas, so i'd say either pulling back the plan some or bringing a stage or another deco gas are all appropriate. i don't think planning on your buddy's gas in a lost gas scenario is enough. i know everyone seems to say 'my buddy has my gas', but it's not something i believe. that extra third is for emergencies, not a guaranteed 'get out from the furthest penetration' card.

however, i'm a new deco diver so the usual grains of salt apply.

 

[Rhone Man]

Some of the tec instructors will weigh in soon enough, but I was always taught you carry a 50% reserve on your bottom gas, and a 50% reserve on your deco gases.

I have never heard of gas planning that requires you to carry enough back gas to accomplish your deco with back gas. And to do so would be almost impossible to do if you were using a hypoxic bottom mix.

 

[Captain12Pk]

Generally speaking you do not plan for two failures (ie, the loss of "Rock Bottom" back gas AND the loss of deco gas). If somehow I lost my deco gas I would begin my deco. obligation on back gas. It's almost certain I'd have more gas left in my tanks than your probably thinking because we planned this dive with "Rock Bottom" protocols. After the first 5 min on deco. my buddy and I would swich. He would go to back gas, I would go to his bottle (EAN50 or o2) and we would continue like this 'till we completed our obligation. Depending upon gas remaining at the end of our deco obligation and sea conditions, we may add on a few minutes to cover ourselves.
Hope this helps.
Remember YMMV.

K

 

[elan]

I'm not trained yet so my opinion is worthless. for me Deco requires redundancy and as such i would limit my bottom time so I could accomplish my deco with the back gas if I lost my deco bottle, or I would have a redundant system for deco gas.

Do not be hard on yourself You make perfect sense

 

[elan]

well, you always have to plan for lost gas, so i'd say either pulling back the plan some or bringing a stage or another deco gas are all appropriate. i don't think planning on your buddy's gas in a lost gas scenario is enough. i know everyone seems to say 'my buddy has my gas', but it's not something i believe. that extra third is for emergencies, not a guaranteed 'get out from the furthest penetration' card.

however, i'm a new deco diver so the usual grains of salt apply.

Yeah this is what my tech instructor says - when doing your planning count only on yourself. One should be self sufficient.

 

[elan]

Some of the tec instructors will weigh in soon enough, but I was always taught you carry a 50% reserve on your bottom gas, and a 50% reserve on your deco gases.

I have never heard of gas planning that requires you to carry enough back gas to accomplish your deco with back gas. And to do so would be almost impossible to do if you were using a hypoxic bottom mix.

sorry forgot to put hypoxic aside.

 

[Randy43068]

you always take a table along for lost gas and usually a table for, say 10 feet more than planned, and one for, say 5 minute more at bottom than planned.

When you do your planning you take into account all the gas you're planning on using plus reserves then you take appropriate size bottles.

If you're laying out a no win scenario then you deco out on what you have, and hope for the best. If your bud has gas at deco and he's willing to share, then, well then he's a really good bud.

I'm sure someone will come along and give you the whole lesson plan shortly.

 

[Randy43068]

Yeah this is what my tech instructor says - when doing your planning count only on yourself. One should be self sufficient.

Not true. Not true at all.