100% Oxygen deco

[Dominic]

Maybe they figure that since you're trying to get rid of the excess Oxygen, breathing a hypoxic mix will just use up the O2 sitting in your body and therefore presents no risk?

[Mark Chase]

It is unlikley that the back gas will be hypoxic even 12/80 would be breathable at 6m because you are at 1.6 atms so it would be tha same as breathing 19% at the surface. When you start droping below 110m it might be considered a problem but I think even 10/80 is breathable at 6 (just) as long as you are not exerting your self so that will get you to 130m.

The only thing I know that does air breaks is the VR3 computer (which prompts them after 80% CNS is reached) and the proplanner that goes with it. Also Vplanner which is a free down load will incorperate air breaks into the profile.

ATB

Mark Chase

[MartinS]

Hi Mark
When doing air breaks on the VR3, I guess you do a gas switch on the computer to air for the duration of the break - have you done any comparison dives without air breaks to see what difference to the deco time it gives, or is reducing deco time not appropriate with air breaks, just stopping the long exposures to high ppO2 the only need to do them.
Sorry if this sounds a silly question - just want to understand more of the sort of diving you do, and I hope to be doing someday.
Regards, and dive safe
Martin

[Mark Chase]

Thats a tough question.

Problem is the VR3 will recommend air breaks as soon as you hit 80% CNS and I am not aware of a way of switching that system off.

The other problem is that you always get a shorter run time on the VR3 than on tables because the VR3 plans deco on what actualy took place and the tables are usualy bassed on max depth or max less about 3m for the end of the dive. As a result any comparison has to be maped with a complicated multilevel profile after the event using the data provided by the VR3.

Surfice as to say I have never bothered doing it

I would add the air breaks to my 6m stop and thats that. If I was on a VR3 and folowing that (asuming my buddy has another VR3 for cros referance or I have two VR3s) I would just do what it told me and kick it arround the room later if it got me bent. At the moment if I am going to do air breaks I would run tables as I havent had enough experaince with the VR3 to trust it that much.

Lets face it, if the dive is such that it warrents exceading the CNS recomendations and risking a CNS hit, who cares about another 15mins in the water if it ensures your wellbeing? A big dive like that is a dangerous thing and I for one dont want to screw up on the easy bit where you just hang in 6m of water doing nothing.

ATB

Mark Chase

[Pierre Farrugia]

<font color='#0000FF'>Hello Mark,

Originally Posted by [b

Quote[/b] ] I would just do what it told me and kick it arround the room later if it got me bent

I like this comment &nbsp;

Mark which copy do you have a ProPlanner ? I have 7.12C

[db8us]

Hi Dudes,

we have some profiles on www.ekpp.org i also posted some here in the forum a few months ago.
Since 2-3 years i do not even calculate the CNS% any longer, because i think they are ok for nitroxdives etc , but not for longish cave-dives. we lower the pO2 in the bottom-time an extended our breakes to 12m on O2 and 8Min off without adding them to the decotime, so the deco stays short.
This is working IMHO with High-He mixes and not with Air/Nitrox-dives...

[TDave]

Originally Posted by [b

Quote[/b] (Mark Chase @ Sep. 15 2003,17:12)]At the moment if I am going to do air breaks I would run tables as I havent had enough experaince with the VR3 to trust it that much.

Why spend X amount of hard-earned pounds on it then?

[Phil Ennis]

<font color='#0000FF'>Because you don't have to be doing air breaks to use a VR3.

How many air breaks have you done?

Get your fuc*ing hair cut.

[Mark Chase]

Originally Posted by [b

Quote[/b] (TDave @ April 18 2004,00:15)]

Why spend X amount of hard-earned pounds on it then?

As Phill said you dont have to do the air breaks recomended by the VR3, but the key word you missed was experance. When I wrote that post (Sep 03) I had only done 6 dives on the VR3 and I was still running tables side by side to ceck it was working corectly.

I have now loged 36 dives with the deepest down to 102m on the VR3 and I quite litraly trust it with my life &nbsp;

I am frankley astonished that any one not limited by the doctrins of DIR or lack of free cash would do Trimix diving without one. They are great bits of kit.

Since writing that post I have made a concious decision to keep CNS down by lowering PP02 at max depth and using 80% for deco. If I do run air breaks I will add them to the total 6m stop time and run 5 in 15min profiles.

ATB

Mark Chase

[TDave]

Phil, you already know I haven't done any air breaks, or dives requiring them, but my question didn't regard that.

My question was aimed more at the element of trust, although, as pointed out, I did fail to pay attention to the date of the original post - problem with posting late at night! - and Mark says he does now trust it completely, which to be honest is what I would expect, and makes sense. And that's fine and answers my question!

TD