PO2 limits...

[ianr33]

But you would need 350 cu ft of nitrox in your tank(s), Charlie.

40% nitrox (recreational limit) 82 1/2 feet (PO2 of 1.4) SAC of 0.4 (low but not ridiculous)

Gas needed 210 cu ft. Heck,dont even need a cave fill in double 130's

Not a recreational dive due to deco though

 

[nereas]

...My main objection to the oversimplification is that too many divers then think of the ppO2 limit as a hard, instantaneous limit, and are unwilling to exceed that limit in an emergency.

My own main objection to the over-complication is that for NDL recreational divers, there effectively is no time consideration. Only for technical divers performing their comparatively extreme types of dives involving decompression do exposure times become a realistic consideration.

At some point, there is a hard bottom to all this.

Is it at 2.0?

Is it at 3.0?

How deep would you go to save me, Charlie?

Or if not me, to salvage my gear and my DPV?

 

[nereas]

40% nitrox (recreational limit) 82 1/2 feet (PO2 of 1.4) SAC of 0.4 (low but not ridiculous)

Gas needed 210 cu ft. Heck,dont even need a cave fill in double 130's

Not a recreational dive due to deco though

At least you do agree that there is no way all that is going to fit into an 80 cu ft tank.

That is what I am trying to get Charlie to see.

 

[ianr33]

At least you do agree that there is no way all that is going to fit into an 80 cu ft tank.

That is what I am trying to get Charlie to see.

Rubbish. just need to fill it to 7800 psi

I do think that Charlie has a very valid point though in that some (many?) divers think that 1.4 is the limit and they will immediately die if they drop below this for a couple of minutes.

 

[Charlie99]

My own main objection to the over-complication is that for NDL recreational divers, there effectively is no time consideration. Only for technical divers performing their comparatively extreme types of dives involving decompression do exposure times become a realistic consideration.

At some point, there is a hard bottom to all this.

Is it at 2.0?

Is it at 3.0?

How deep would you go to save me, Charlie?

Or if not me, to salvage my gear and my DPV?

Actually, if you go through the numbers, using the NOAA Exceptional Exposure limits, with EAN32 I will always run out of gas first when diving an AL80. With EAN36 or EAN40, that's not always true. For a buddy that is worth saving, I'd have no qualms about going to 2.0 or even 2.5 for 5 minutes or less.

For you I'd go to 1.4.
For your DPV I would go to 1.6ata, but for no longer than 45 minutes.

To put things into perspective, with EAN36, ppO2 of 2.0ata is 150'. With EAN32, ppO2 of 2.0ata is 173'. Even when diving nitrox, my true absolute rock bottom is the limiting factor in an emergency rescue, not MOD.

 

[GoProHonduras]

Hi All,

Myself and a team mate just ran this profile today, we're in the tropics and have no problems with these run times or O2 exposures.

Not saying it is right or wrong, but it works for us and we're in moderate fitness.

V-Planner 3.72 by R. Hemingway, VPM code by Erik C. Baker.

Decompression model: VPM - B

DIVE PLAN
Surface interval = 1 day 0 hr 0 min.
Elevation = 0ft
Conservatism = + 2

Dec to 110ft (1) Nitrox 32 60ft/min descent.
Dec to 200ft (3) Trimix 14/50 60ft/min descent.
Dec to 300ft (5) Trimix 14/50 60ft/min descent.
Level 300ft 15:00 (20) Trimix 14/50 1.41 ppO2, 119ft ead, 133ft end
Asc to 220ft (22) Trimix 14/50 -30ft/min ascent.
Stop at 220ft 0:20 (23) Trimix 14/50 1.07 ppO2, 82ft ead, 93ft end
Stop at 200ft 2:00 (25) Trimix 14/50 0.99 ppO2, 73ft ead, 83ft end
Stop at 180ft 2:00 (27) Trimix 14/50 0.90 ppO2, 64ft ead, 73ft end
Stop at 160ft 3:00 (30) Trimix 14/50 0.82 ppO2, 55ft ead, 63ft end
Stop at 140ft 2:00 (32) Trimix 14/50 0.73 ppO2, 46ft ead, 53ft end
Stop at 130ft 3:00 (35) Nitrox 32 1.58 ppO2, 107ft ead
Stop at 100ft 1:20 (37) Nitrox 32 1.29 ppO2, 81ft ead
Stop at 90ft 2:00 (39) Nitrox 32 1.19 ppO2, 73ft ead
Stop at 80ft 3:00 (42) Nitrox 32 1.09 ppO2, 64ft ead
Stop at 70ft 3:00 (45) Nitrox 32 1.00 ppO2, 56ft ead
Stop at 60ft 4:00 (49) Nitrox 32 0.90 ppO2, 47ft ead
Stop at 50ft 5:00 (54) Nitrox 32 0.80 ppO2, 38ft ead
Stop at 40ft 8:00 (62) Nitrox 32 0.71 ppO2, 30ft ead
Stop at 30ft 11:00 (73) Nitrox 32 0.61 ppO2, 21ft ead
Stop at 20ft 10:00 (83) Oxygen 1.60 ppO2, 0ft ead
Stop at 20ft 2:00 (85) Nitrox 32 0.51 ppO2, 13ft ead
Stop at 20ft 10:00 (95) Oxygen 1.60 ppO2, 0ft ead
Stop at 20ft 2:00 (97) Nitrox 32 0.51 ppO2, 13ft ead
Stop at 20ft 8:00 (105) Oxygen 1.60 ppO2, 0ft ead
Surface (105) Oxygen -30ft/min ascent.

Off gassing starts at 237.7ft

OTU's this dive: 127
CNS Total: 91.2%

2975.6 ltr Trimix 14/50
1244.0 ltr Nitrox 32
452.7 ltr Oxygen
4672.3 ltr TOTAL

I think the whole CNS clock needs to be relooked at, too many variances that can come into effect, environmental factors, physical condition of divers etc.....

Bottom RMV was 12 litres per minutes, miniscule current in the shallows, so a 10 litre RMV was calculated.

 

[GoProHonduras]

Sorry in cubic feet that's 0.42 for work and 0.35 for rest, and in general higher PO'2s have been touched before.

 

[SkubaJim]

What kind of wine?

Have you ever tried "retsina"?

Nah, only the Greeks can drink that stuff.

 

[jviehe]

Ill plug PADI a bit here. Pick up the Encyclopedia of Recreational Diving for more info, AND of course take a nitrox class. They physics behind diving is pretty interesting, including deco theory.

 

[jsado]

ummm.....yeah...thanks? I really appreciate all the info and I'm sure one day it'll all make sense. I guess what I'm concerned about is....as a recreational diver who has yet to break the triple digit ft. barrier, do I need to worry about this yet?