Basic decompression questions

[Thalassamania]

And what were you doing? We want the story!

No big deal, a couple of days in Jules Undersea Lodge (the old PRINUL, 24 FSW to the moonpool interface), then up to the surface at 60 FPM.

 

[eponym]

1. Is there no risk at all of decompression sickness when diving 20 ft or less?
2. Is there anycway to expedite the process of removing excess nitrogen from your body after a dive?

You don't say it, but are you thinking flying after diving? I had this question once (had a flight out scheduled just after a class). I called the DAN info line and was pleased to get a very frank answer from a medical professional which set my mind at ease.

Cheers,
Bryan

 

[String]

Or dive, but don't surface

Good point - that alternative solution completely escaped me

 

[Rick Inman]

I called the DAN info line and was pleased to get a very frank answer from a medical professional which set my mind at ease.

Please share with the class. What was the "frank" answer? - (although I can guess)

 

[Walter]

how many cycles did you consider "full saturation"?

Generally, six cycles is considered full saturation, that puts the compartment in question at 98.4375% saturation. Longer exposure doesn't alter that percentage significantly. If he spend a couple days at depth, that would account for a 480 minute compartment being "fully saturated".

 

[kgault]

Check out: NMRC 02-01 entitled "Multi-day air saturation at 20 and 22 fsw with direct ascent: Data Report on Project 92-09" by R.W. Bill Hamilton, Edward D. Thalmman, and Diana J. Temple.

Available from the Rubicon Foundation at Rubicon Research Repository: Item 123456789/4585

In the background section it states "Decompression sickness (DCS) has been reported after saturation at depths as shallow as 25.5 fsw. Dives to depths of 20.0 to 21.3 fsw have had no DCS in 75+ man exposures".

Hope this brightens up the discussion ;>

Keith

 

[Blackwood]

Generally, six cycles is considered full saturation, that puts the compartment in question at 98.4375% saturation. Longer exposure doesn't alter that percentage significantly. If he spend a couple days at depth, that would account for a 480 minute compartment being "fully saturated".

I've alternately seen 5 and 6 cycles considered "full saturation." That's only what, a 3% difference (give or take)?

But yah, I'm not arguing. Wasn't expecting a multi-day stay. Thought he was on a long dive.

 

[Walter]

I've alternately seen 5 and 6 cycles considered "full saturation." That's only what, a 3% difference (give or take)?

Look at the Navy tables, they are based on a 120 minute compartment. They clear in 12 hours. One cycle = 2 hours. Two cycles = 4 hours. Three cycles = 6 hours. Four cycles = 8 hours. Five cycles = 10 hours. Six cycles = 12 hours. You can see the same principle with the RDP and it's 60 minute compartment clearing in 6 hours. Six cycles is fairly standard.

 

[Blackwood]

Look at the Navy tables, they are based on a 120 minute compartment. They clear in 12 hours. One cycle = 2 hours. Two cycles = 4 hours. Three cycles = 6 hours. Four cycles = 8 hours. Five cycles = 10 hours. Six cycles = 12 hours. You can see the same principle with the RDP and it's 60 minute compartment clearing in 6 hours. Six cycles is fairly standard.

I recall from one class or another seeing tables with 5 cycles. Would probably have been TDI or IANTD.

Also could have been 7 cycles. I don't remember.

(It was obviously very important)

 

[mikeyjoe]

Is there anyway to expedite the process of removing excess nitrogen from your body after a dive?

I believe a post dive meal of chilli and beer will accelerate off-gassing......