What gas do you typically use for deco?

[jptaylor9]

I typically deco on 70%, or that's at least what I ask my dive shop for!

[Reeve]

If I'm pottering with a single 15L I use a 3L 50mix front mount, usually as a safety margin and if required can be breathed from 30m while ascending. If I'm planning a specific deco dive I'll use 80% in a 7L.

[Pierre Farrugia]

I use 60% (ideal 64%) as this will give me a deco of a >PpO2 of 1 bar all the way up.

Using Nitrox 64 for deco

15m * ppo2 1.6
12m * ppo2 1.4
9m * ppo2 1.14
6m * ppo2 0.96

[Mark Chase]

I am on CCR now but I used to use 80% for deco. Main reason was the flexibility of the final stop depth. Doing long deco hangs in the fast tidal currents off of Dover we were forced to deco on the shot to avoid getting run over by car ferry’s. This often meant doing your last stop deeper than the optimum and 100% was useless. Other problems with getting good fills on 7ltr stages also forced the move to 80%. I just ditched the 3m stop and did all my long hang deco between 9 and 6m. It worked for me.

Note: I almost always took a second stage of 32% for intermediate deco and bail out. 90% of my diving is Trimix with 45min to 120min hang times. On a Nitrox or Air deco dive I would probably not bother and just use a stage of 50%.

ATB

Mark Chase

[Sandman]

I used to use 80% on my shallow stop. Now I am on 1.3 which is very nice.

Cheers

Simon

[jlwarlow]

On the last trip I was on (which was 1st after getting my Advanced nitrox cert) I had 50% in a 3L pony. I've since been given some advice for using 36% in my pony so that a) It gives me a safety margin for deco (as long as main cylinder has < 36%) and b) I can bail out to the pony at 30m where's 50% can only bail out <20m

[Reeve]

Originally Posted by jlwarlow

On the last trip I was on (which was 1st after getting my Advanced nitrox cert) I had 50% in a 3L pony. I've since been given some advice for using 36% in my pony so that a) It gives me a safety margin for deco (as long as main cylinder has < 36%) and b) I can bail out to the pony at 30m where's 50% can only bail out <20m

IMO using a ppo2 of 2 you could comfortably bail out at 30m on a 50% mix. Granted it's a little higher than 1.6 but for the small amount of time, you're breathing the mix below 20m is minimal.

[RichClark]

I've settled on my own standard gases, and they tend to be 32% for travel (and bail out) and 80% for deco.

I'd probably use 100% in an ideal world, but unfortunately the english channel is far from ideal so 80% suits my diving much better.

Cheers

Rich
PS saying that, my best dives have always been at home in the UK

[gobfish1]

I typically deco on 100% on dive,s in 35m/50m air / nitrox dives

all so use 30% 40% 50% 64% 73% 85% as and when it suit,s my dive

10L cylinder 50%nitxox on the line is good when it all go,s t*ts up

steve

[Davey Willo]

Originally Posted by jlwarlow

On the last trip I was on (which was 1st after getting my Advanced nitrox cert) I had 50% in a 3L pony. I've since been given some advice for using 36% in my pony so that a) It gives me a safety margin for deco (as long as main cylinder has < 36%) and b) I can bail out to the pony at 30m where's 50% can only bail out <20m

Hello there

I hope you don't mind me saying but I feel that the advice you were given is flawed, it would appear that you're not able to decide on whether you want a redundant air supply or a deco gas for accelerating your deco.

Trying to get one 3ltr pony bottle and one gas mix to achieve both goals is asking to much, you really need to make a decision and go with it.

Obviously after your recent training you're aware that we need to maximise the o2 window to achieve the accelerated deco that we desire, usually trying to initially achieve a ppo2 of 1.6 bar to flush out the nitrogen.. on 32% this would be in the region of 40m

So we can see that 32% is fundamentally useless as a deco gas unless you're coming up from some serious depths with serious obligations and I don't get the impression that that is the case.

I'm not having a go here J, so please don't think I am, I just cannot see the logic of the advice you were given.

Should you be diving in the 30m range with no obligations apart from safety stops then your pony is sufficient (only just) as a redundant air supply but the fact that you mention taking 'Advanced Nitrox' would indicate that you intend to push depths and or times incurring deco obligations.

If that assumption is correct then you really need to start thinking of a manifolded twinset (This adds the redundancy and removes the need for an AAS) and then you need to calculate how much gas you would need for the required deco that you intend to complete in the future and I'd be very suprised if a 3ltr pony was anything like enough.

If you intend to dive deeper/longer than consider twins and consider a 7ltr luxfer for deco.

Remember once you and your buddy have incurred deco obligations then both of you should be carrying enough gas to make sure that you or your buddy can come out on back gas should you lose a deco gas..

Bite the bullet mate, sell your stuff, sell your soul, whatever it takes but if you intend to do more intense diving then go properly equipped, if you can't afford it just yet then wait, the dives will always be there.

Best regards
Dave.