Standard Bailout Mixes

Steve

Do any of the training agencies nominate standardised bailout mixes? Standardised mixes are the go in the DIR church but these mixes don't necessarily fit the specific needs and operation of Closed-Circuit Rebreathers all of the time. Am I having a blonde moment thinking that we can come up with a best all round list of gasses or is it too depth and location specific?

What is your bailout gas list and why?

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Philippe GERIN

Why not? and why not use the same mixes?
bailout bottom mix = dil = 21/35 or 18/45 => S80
Nitrox 50 => S40
100% O2 => S40
Fits most of the "reasonnable" profiles from surface to the 70m range for the average CCR diver.
Best
Philippe

wedivebc

I always felt standard mixes leave you with less than optimal gas for many dive plans. For OC diving I was never a fan of it. Since we sometimes use team bailout with CCR it may be worth a second look. I am not sure all my objections to standard mixes hold up as well in this application.
I will be watching this thread with interest.

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Dave....

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diverreb

On all Dives up to 170', which are 95% of all dives I do, I use a 20/50 Dil with a second stage plumbed into the onboard dil to use if there is gas available and a QC second stage that can be connected to the manual O2 fill hose for use at 20', again assuming there is gas available..

On dives in the 75' - 105' range I add a 40CF bottle of 28/40.

On dives in the 110' - 140' range I add a 40CF bottle of 70% to the above.

On dives in the 150' - 170' range I take an additional 40CF Bailout of 24/40 along with the 28/40 because that's what I need to get back to the anchor and up to 40' where the deco gas is hanging.

As to the why... It's much easier to find a Bailout mix that will fit the majority of dives you do so you aren't constantly dumping a remixing Bailouts for every dive or if you have a bunch of premixed bottles possibly grabbing a Bailout mix that may be to rich for a particular dive.

The primary dive boat I use actually chains the hook into the wreck so it's always in place. The boat hangs 4 regs of 70% at 40' so I figure I have enough gas to get up to those regs on the 150' and deeper dives.

When diving on other boats that don't use a highly secure method of staying attached to the wreck I'll add a 40CF bottle of 70% and drop it next to where I tie my wreck reel off, if I'm carrying two Bailouts and I'll keep it with me if I'm only carrying one bailout.

Richie

warjarrett

I am a new rebreather diver, with no He experience, so I have to stick to basic questions here. But it is obvious to me that bailout requirements are VERY different for O2/N2 OC, He/O2 OC, O2/N2 CC, and He/O2 CC divers. For any O2/N2 diver, why not just plan your max depth and choose the bailout's FO2 to give you 1.4 PO2 at that depth? But then for CC, some accidents are caused by over-exposure to O2, so would a lower PO2 make sense for CC divers?

decoweenie

Since we are talking about bail-out gas, are you going to dump full stages and mix for every dive if you don't standardize your gas ?

Personally, I use the same set of bail-out tanks because of these local-specific reasons (and they might not apply to others):

• Our week-end wrecks are in 72m, 85m, 92m and 115m.
• It is not 100% guaranty that we will be able to dive a specific wreck until we got out to the primary site (due to local-specific reasons), so must be able to divert to secondary site. Or go home.
• Many times we were forced to dive the shallower wrecks using the higher He mix when can't dive the deeper ones. This just meant slightly longer deco.

So I use 10/50 + 50% for bail-out, except 10/70 + 50% for the 115m site. Same trimix for on-board.

I usually penetrate the wrecks so using a hot-mix to save deco isn't ideal as I wouldn't be able to commence the ascend immediately upon bailing out.

First team hangs a spare trimix stage at bottom of anchor line, last team removes it. There are plenty more of safety stages on the boat to drop when an yellow DSMB is sent up.

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IN468

If you take a MOD 2 CCR Trimix course you will learn that your diluent for bottom should have max pO2 of 1,0 so that you can lower pO2 by a diluent flush

decoweenie

Which agency teaches this ?

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steveharriss

Not sure which agency teaches it but it is there in the Tek Rebreather book of which Tom Mount was a co-author so maybe IANTD?

UKSteve

There is a difference in approach for the selection of diluent for a given depth and the bailout gas from a different depth. Unless your bailout is plumbed into your loop and you plan to use it as such I cant see the low ppO2 requirement to be valid for the bailout gas (which is what this thread is discussing)

Down to 30m I use Nitrox 21 for bailout (where I am using Nitrox 21 dil) and then down to 70m I use 18/45 and Nitrox 50 in conjunction with 10/50 diluent (I have that inboth steel 7s and Al 80s and select the ones I need dependant on planned depth and deco intentions - steel 7s cos I already had them!). Not done serious diving below that depth yet on CCR.

Its nice when your buddy is carrying the same.. what's mine is mine and whats his is mine without any extra fiddling with tables, deco computers etc!

Steve