Shallow Decompression Dives

[Reg Braithwaite]

With a mix of 32/15 I can do a dive to 80fsw for 80 min and surface with only a 3 min obligation on back gas, I would hardly call that deco diving

Just out of curiosity, where did you get the figure of three minutes's deco for a dive on 32/15 to 80fsw for 80 minutes?

 

[Kevrumbo]

NAUI RGBM Tables for 30/15 Helitrox with 80fsw for 80min:

Deco Profile on Backgas:
(max ascent rate 33fpm)
30' 4min
20' 11min
10' 20min

The only way you can get a three min deco obligation (at 10fsw) for 80fsw depth is a bottom time of 30min . . .
--

 

[jtivat]

Just out of curiosity, where did you get the figure of three minutes's deco for a dive on 32/15 to 80fsw for 80 minutes?

Well if you run V-Planner at nominal conservatism and use O2 for deco you can get that profile.

 

[Blackwood]

IANTD's EAN32 table calls for 25 minutes deco after 80 for 80. I don't have any IANTD mix tables handy, and can't remember off the top of my head whether or not they punish you for helium.

 

[Kevrumbo]

Minimum Deco (Ratio Deco) for 30/30 mix, 80' for 80min on backgas only:

60' 1min
50' 1min
40' 3min
30' 6min
20' 11min
10' 24min

(Is this a Ginnie Springs Cave dive profile?)

 

[Reg Braithwaite]

IANTD's EAN32 table calls for 25 minutes deco after 80 for 80. I don't have any IANTD mix tables handy, and can't remember off the top of my head whether or not they punish you for helium.

I happen to have an IANTD 32/15 table handy thanks to having just taken their Recreational Trimix course. I am neither endorsing nor refuting their table, just repeating what I think it tells me: 80fsw for 80min, 32/15 Trimix: 10 minutes at 15 feet on back gas, or 7 minutes at 15 feet on EAN50. The table claims to be based on VPM-B as calculated using V-Planner. 30fpm ascent rate, nominal conservatism.

 

[Blackwood]

I happen to have an IANTD 32/15 table handy thanks to having just taken their Recreational Trimix course. I am neither endorsing nor refuting their table, just repeating what I think it tells me: 80fsw for 80min, 32/15 Trimix: 10 minutes at 15 feet on back gas, or 7 minutes at 15 feet on EAN50. The table claims to be based on VPM-B as calculated using V-Planner. 30fpm ascent rate, nominal conservatism.

EAN50 at 15 feet? Any option for Oxygen?

I wonder what they were thinking when they built those tables...

 

[PfcAJ]

Minimum Deco (Ratio Deco) for 30/30 mix, 80' for 80min on backgas only:

60' 1min
50' 1min
40' 3min
30' 6min
20' 11min
10' 24min

(Is this a Ginnie Springs Cave dive profile?)

No, not the best idea for a cave deco schedule. If you have an issue and lose/ use all your BG, you probably won't get out of the water without getting bent to some degree. There just won't be enough gas to complete that obligation.

 

[Kevrumbo]

Yeah that's true. . .

Probably better on three stage AL80's, with double 130's and O2 deco?

60' 1min
50' 1min
40' 3min
30' 7min
20' 15min [O2 Switch]
10' 3min
-->surface 3min

 

[ucfdiver]

Given that all dives are decompression dives, whether taught that way or not, and that DCS is rare it seems to me there is too much emphasis on the need for extensive "special" deco training.

Stop kidding yourself. DCS just isn't talked about. People are getting bent left and right. 5 divers at Ginnie springs alone were bent last month, all "undeserved" hits according to whatever tool they were using for deco...and we're not even bringing up the "oh I'm not bent, I'll just go to bed or go have a beer" cases.

Look here where 43% of 237 cave divers reported they had been bent
Have you gotten bent? - Cave Diver's Forum

I was told during full cave point blank that I'd get bent eventually. Recently my dive buddy got bent a few weeks back on the same tables (2 minutes different from a previous profile). A 119min dive at Ginnie, about 85ft average, with 35/85GF tables with added time at deep stops, swimming up the spring run on o2 for cushion there, and a generous amount of time on the surface before exiting. Too many people are scared to talk about DCS in my opinion, and it gives divers a false sense of security.