Deep safety stop question

[Dr Deco]

Hello Bowzer:

All gas loadings for all recreational dives are covered by tables. The 5 to 120 minute compartments will be tracked. It is not necessary that a compartment be saturated, only necessary that its loading exceeds the limit for direct ascent.

Other than Jollie Bookspan’s book, there others that you can find on Amazon books. You will find some like “others who bought this book also bought.” There are other books then that you can pickup

Dr Deco :doctor:

The next class in Decompression Physiology for 2007 is August 18-19. :1book:
This class is at the USC campus in Los Angeles.
http://wrigley.usc.edu/hyperbaric/advdeco.htm

 

[Gene_Hobbs]

The 5th through 11th articles on the DAN Europe Medical Articles page are all about a series of tests on different ascent profiles from 82' 25minute + 82' 20 minute repetitive dives. A limited number of trials, not the profiles I would have chosen to test, and only done at one depth, but it is a set of data that is real.

Funny, I recognized a few papers on that list.

As for the DAN-E paper, when it was published in Undersea and Hyperbaric Medicine, there was a letter to the editor and reply that are worth a read. I did not see those on the list. Those can be found here.

The work at NEDU is being written up now and will be published in a few months. This is using the BVM3 Model. The UHMS abstracts have leaked out around internet but I will not add them to the database until they are actually published.

As for reading materials, we have started a "Suggested Reading List" for materials held in the Rubicon Research Repository.

Systematic Guide to Decompression Schedule Calculations.
Braithwaite. 1972
RRR ID: 3945

used with:
CALCULATION OF DECOMPRESSION SCHEDULES FOR NITROGEN-OXYGEN AND HELIUM-OXYGEN DIVES.
Workman. 1965
RRR ID: 3367

 

[nereas]

Wow, lots of interesting reading in this thread. Thanks to all.
One of my reason for starting this thread is that I have a significant difference in gas consumption in cold vs warm water. I normally dive Lake George NY, etc. (cold, dark) and have a SAC of .7 +/-. When in FL waters last summer my SAC went to .45 (cold, low viz and lots of weight/rubber makes quite a difference). The difference leads to a major change in how long I can go on a tank. I dive an Aries computer and use YMCA tables as backup. Even on EAN32, it is possible to get into N2 loading areas that I am uncomfortable with, especially on 3 tank dives with little sit out time. The air divers on the same dives had to be way past what I would consider safe. This got me looking into deco and just where the safe line is between the "recreational safety stop" and "deco". I picked up a copy of Wienke's book and while I can follow it, calculus was too many years back to do the math. I do plan my dives in a general way, but with rec diving the level of planning that tech divers go to isn't justified and often the boat will divert to another site.
What I would like to do is to find a simple, effective, generally agreed to, formula that I can put into table form and keep on my slate for recreational purposes. While every training agency has created recreational tables, most are rather shy on deeper "recreational" stops. I assume it is a liability thing, or else they are loath to admit a safety stop is a decompression stop.

Bowzer, there are better nitrox mixes than EAN32 for dives above 100 fsw.

Try EAN36 a time or two and see how you like it.

 

[Charlie99]

I thought that 5 and 10 minute compartments were the primary ones that rec tables were based upon as these were the ones that were libel to reach high percentages of saturation during one tank dives and that the longer compartments were what came into play with double tanks, etc. ........

........ Can you provide me info on some references to read.

The 5 and 10 minute compartments also have higher limits than do the longer halftimes. A good article to read to understand basic dissolved gas model is "Understanding M-Values" by Eric Baker. The m-value table is for ppN2 in absolute feet-saltwater. I mention this because when I first read the article, nothing made sense until I figured out that a 5 min PADI/DSAT m-value limit of 99fsw was really 99fsw-absolute. Just like relativistic mechanics more sense after one has a firm grasp of Newtonian mechanics, a firm grasp of neoHaldanian dissolved gas models makes understanding dual phase (i.e. "bubble") models easier.

For a better intuitive understanding of what is going on, I converted the M-values into depths on air. For example, if one goes to 94' on air, the 5 minute compartment would approach but never exceed its limit, no matter how long you stayed at 94' depth. This table is for the DSAT/PADI model, but Erik Baker's article has limits for several other models (and also in metric units) if you prefer.

5 minute compartment limit = 94' on air
10 min = 73' on air
20 min = 53' on air
30 min = 44' on air
40 min = 39' on air
60 min = 34' on air
120 min = 28' on air
480 min = 23' on air

In an earlier post I walked through examples of what is going on in various compartments for both an air dive to 100' and one to 80'. In that post, I converted both the limits and compartment loadings to equivalent air depths for ease of understanding.