Deco at 6m vs 3m times inversion

[Kevrumbo]

Thanks guys, that is what I was thinking.

Are you staying as well longer at 30ft /10m . . . ??

Well . . . I did open-circuit Oxygen at 30feet/9meters depth for over an hour (an Oxygen ppO2 of 1.9) during an In-Water-Recompression (IWR) session in Oct-Nov 2014, with interval relieving Air Break gas switches. (The IWR was performed off the end of Truk Stop Hotel Pier lying prone & relaxed at 9m depth on a sandy bottom in 28 deg C water temp, and the profile schedule took another two-and-a-half hours just to surface).

I was effectively "de-nitrogenated", as well as relieved of type I DCS symptoms. . .

 

[LiteHedded]

I do the bulk of oxygen time at 20ft.

I find a slow ascent from 20 to the surface to be beneficial, and that usually turns into 'stops' at 15, 10, and 5.

I just do the shortest deco my buddy will allow and get out of the water

 

[Gareth J]

In the UK the planned stop depth is normally 6m, this is because surface conditions are likely to be such that a 3m stop is not possible to hold. We are prone to heavy wave action and large swells.
So, when planning dives 6m is used because it's the worst case, on the day ( or probably more accurately, at the end of the dive), if conditions allow the stop may well move to a shallower depth - this is one of the advantages of dive computers over hard tables.
I still carry a set of hard tables for mixed gas dives, with the planned dive, an overrun, and a loss of travel or deco gas . These are always planned with a 6m stop. Where conditions are kinder, I have been known to plan with 4.5 or 3m stops.
;
On CCR, the bailout deco mix is seldom 100% O2, it's a matter of logistics and what you can carry. The bailout gas can be a hot bottom gas - a PO2 of 1.6 or potentially higher - if I'm forced to bailout, I would normally be going up, not hanging around at depth, so the PO2 will be crashing. So you want / need to get off the bailout gas and onto the deco gas, waiting until 6m is not viable.

Planning deco gas is often dictated by conditions, volumes need / able to be carried, and what's available. High pressure O2 is not always available.

Gareth

 

[Michael Guerrero]

If it's easy to hold the 10ft stop due to conditions or dive location, I prefer that for the lower ppO2 since O2 does bad things to the human body. If 10ft is going to be squirrely, 20ft with a slow crawl to the surface after the obligation is fulfilled is just fine.

 

[Remy B.]

My instructor considers the 80% Deco mix the best, but he does the 3m stop, For what I have been playing with the Software, Deco mix of 80%, seems the best, no much difference compared to 100%, but it allows for the 6m Deco stop, with margin of PPO2, I differ with my instructor as I will prefer to be at 6m and not at 3m Stop, he likes to keep the PPO2 very low, as I will prefer to keep the bubbles smaller vs a little higher PPO2.

 

[Macan]

The probability of DCS is the same whether you do your final deco stop at 6 or 3 meters while breathing pure O2. But although very rare, you are more susceptible to OxTox with a O2 partial pressure of 1.6 at 6 meters than at 3 meters where the O2 partial pressure is at 1.3.

If the surface conditions are rough, I do my final stop at 6 meters. Else, it's at 3 meters. In either case, it's a slow, 30 seconds to 60 seconds per meter ascent to the surface after completing all deco obligations.