What is a deco bottle?

[Michael_Lambert]

alohagal,

What you are asking now would be explained to you in a Decompression Procedures course. There are calculations that would have to be made as well as a dive plan created with backup plans in place.

One would plan a dive to a depth for a length of time and have to plan the required mix they wish to use for deco and at what depths what mixes will be used for how long.. Keeping in mind like nitrox decompression gas mixes are limiting on breathing depths.

 

[Cleavitt]

Okay...I know the difference now between the gases in a Deco bottle versus a backgas! Which makes complete sense.

Three more questions:
1. Are cavers usually using Nitrox for back gas?
2. Do you adjust computer after switching to 49% through 100% O2 Deco Bottle? Or relying on your brain to make these adjustments to account for proper Deco time?
3. What are the mechanics involved in switching? Just putting the Deco bottle REG in your mouth a turning on the valve? Are you hooking it up to your mount in anyway?

1. Yes, typically Nitrox. Trimix for deeper dives where nitrogen narcosis is a concern.
2. Many cave divers have computers that support multiple gas mixes. They program the computer with the gases they intend to carry before the dive and switch to those gases during the dive. The computer will adjust the deco schedule based on the gas being used. Other cave divers use tables or pre-calculated dive plans for their decompression. The computer is more effecient because in a cave you can't always stick to a pre-planned depth consistently since you are following a cave passage.
3. You clip the deco tank to your harness, usually to one side or the other. Most buddy teams use a protocol that requires confirmation from the buddy before they make a gas switch. This reduces the chance that a diver will switch to the wrong gas at the wrong depth which can be fatal. Once confirmed, the diver just opens the valve and switches regs. It's a completely independent tank and reg set.

 

[H2Andy]

1. Are cavers usually using Nitrox for back gas?

generally yes ... here in Florida, using Nitrox maximizes dive time, since the caves tend to be (with a few notable exceptions) on the shallow side ...

however, for deeper and/or longer cave dives, trimix is used (trimix is a helium, nitrogen, and oxygen mix)

2. Do you adjust computer after switching to 49% through 100% O2 Deco Bottle? Or relying on your brain to make these adjustments to account for proper Deco time?

there are two ways to do it:

a. you plan your dive so you know how many minutes you have at x mix, how many minutes at y mix, etc. and then you follow that plan (this is the preferred method of experienced cave divers); or

b. you use a multi-gas computer which can track x gas mixtures (mine can track 7) and change the mix on the computer as you change mixes in real life. this generally is a backup method, and it's how i use my computer.

3. What are the mechanics involved in switching? Just putting the Deco bottle REG in your mouth a turning on the valve? Are you hooking it up to your mount in anyway?

either you are carrying the bottle with you or you have left it behind.

if you are carrying the bottle, you just put that regulator in your mouth and stow the one you were using.

if you have left the bottle behind, you do the same but clip the bottle to your harness as you get to it.

 

[paddler3d]

there are two ways to do it:

a. you plan your dive so you know how many minutes you have at x mix, how many minutes at y mix, etc. and then you follow that plan (this is the preferred method of experienced cave divers); or

b. you use a multi-gas computer which can track x gas mixtures (mine can track 7) and change the mix on the computer as you change mixes in real life. this generally is a backup method, and it's how i use my computer.

I don't mean to hijack this thread.

I do have a question about this and it is something I just don't understand.

Overwhelmingly any tec diver I have talked to bascially seems to prefer to use tables to plan the dive and dive the dive, with a real expensive multi-gas computer as a back up.

We trust computers for just about anything else in life, so why don't most tec divers use tables or the various software out there to plan the dive, but actually use their real expensive multi-gas computer to dive the dive and then tables with a bottom timer as backup?

 

[mrfixitchapman]

The batteries never go dead on the tables.

DC

 

[DA Aquamaster]

I don't mean to hijack this thread.

I do have a question about this and it is something I just don't understand.

Overwhelmingly any tec diver I have talked to bascially seems to prefer to use tables to plan the dive and dive the dive, with a real expensive multi-gas computer as a back up.

We trust computers for just about anything else in life, so why don't most tec divers use tables or the various software out there to plan the dive, but actually use their real expensive multi-gas computer to dive the dive and then tables with a bottom timer as backup?

Even if you use a computer, you need to ensure you have enough back gas, enough deco gas and enough reserve back gas to do the deco if for some reason you lose one of your deco gasses.

Sio in effect, you need to plan the dive with tables in one form or another anyway to get an accurate estimate of the back gas and deco gas required even if you use a dive computer to do the actual dive.

This is particularly important in cave diving as you not only have a soft overhead (deco obligation) but also a hard overhead that prevents you from going shallower to conserve gas or to abort the dive early as could be done in an ocean dive. So the planning needs to be much more extensive, much more accurate and a 1/3rd reserve is pretty much the minimum for back gas and you normally carry 1.5 times the deco gas you plan to use.

 

[H2Andy]

so why don't most tec divers use tables or the various software out there to plan the dive, but actually use their real expensive multi-gas computer to dive the dive and then tables with a bottom timer as backup?

it's not practical

before you even get in the water, you're going to need to know depth, time, gas mixes, etc. this implies pre-dive planning.

computers are excellent at keeping track of your ongoing dive, but fairly useless in terms of planning a dive

thus, it makes more sense to plan the dive and have it all set up, and then use your computer as a back up rather than the other way around

you could, of course, use the computer as a timer so long as you stick to the dive plan and use the "deco" information the computer is giving you for informational purposes only

the point is that you should know what your dive is going to look like long before you get in the water; once you're in the water, you don't really need a computer anymore.

 

[paddler3d]

it's not practical

before you even get in the water, you're going to need to know depth, time, gas mixes, etc. this implies pre-dive planning.

computers are excellent at keeping track of your ongoing dive, but fairly useless in terms of planning a dive

thus, it makes more sense to plan the dive and have it all set up, and then use your computer as a back up rather than the other way around

you could, of course, use the computer as a timer so long as you stick to the dive plan and use the "deco" information the computer is giving you for informational purposes only

the point is that you should know what your dive is going to look like long before you get in the water; once you're in the water, you don't really need a computer anymore.

Aside from the dead battery thing, but that is what a backup computer is for.

I totally understand what you are saying.

You need to plan the dive to make sure your bases are covered, i.e. you've got the gas for the dive.

To me, I would plan the dive, make sure I've got the appropriate gas for the dive I want to do, but use the computer for the dive.

I know deco adds up quickly, but if you end up not diving as deep as planed your plan is going to be overly conservative and your computer will do the real time math for you and reflect this.

From the tec guys I've talked to they plan out their dive, write their dives on their slates or whatever, pop on the bottom timer and the $1600 multiple gas computer and off they go and really only dive the bottom timer.

I guess why buy the $1600 computer?

It seems that tool, 'expensive computer', is not really being utilized.

 

[ucfdiver]

Aside from the dead battery thing, but that is what a backup computer is for.

I totally understand what you are saying.

You need to plan the dive to make sure your bases are covered, i.e. you've got the gas for the dive.

To me, I would plan the dive, make sure I've got the appropriate gas for the dive I want to do, but use the computer for the dive.

I know deco adds up quickly, but if you end up not diving as deep as planed your plan is going to be overly conservative and your computer will do the real time math for you and reflect this.

From the tec guys I've talked to they plan out their dive, write their dives on their slates or whatever, pop on the bottom timer and the $1600 multiple gas computer and off they go and really only dive the bottom timer.

I guess why buy the $1600 computer?

It seems that tool, 'expensive computer', is not really being utilized.

Computers get to be a PITA when everyone is on a different deco schedule...

 

[paddler3d]

Computers get to be a PITA when everyone is on a different deco schedule...

Okay, I can see that.

I guess my question is for people doing extended deco dives using multiple gasses, do you have a computer or just bottom timers?

Seriously, trimix computers are really expensive.