Safety stop at 15'..........always

[Thalassamania]

Well, it's certainly not for your buddy in the case that he has an equipment failure (as we've learned in the past week or so).

You must be confusing me with someone else, someone selfish and cowardly.

Anyone can have my air, any time, all they want (at least all I've got).

Besides, 3@15 never requires more than 100 psi or so ... plenty go around. Any comrade diver who suffer an equipment failure at 15 feet, at the end of a dive, and who does not have a decompression obligation, is quite capable of getting to the surface with minimum risk, with or without my assistance.

 

[Jim Kerr]

I do a "safety" stop whenever practical, isn't that what the 500 PSI reserve is for? Hanging under that boat and off gassing? Gas does no good whatsoever when left in the tank just so that the DM will think that you a right guy.

It's always been my understanding that the 500 psi is only to ensure that no water can get in the tank, not for the safety stop. They always tell you to be "back" on the boat with 500 psi. So that means to me that after you've done your SS, you should have 500 psi left in your tank. I'm not debating this with anybody, I'm just stating how I interpret it. :20:

 

[Thalassamania]

It's always been my understanding that the 500 psi is only to ensure that no water can get in the tank, not for the safety stop. They always tell you to be "back" on the boat with 500 psi. So that means to me that after you've done your SS, you should have 500 psi left in your tank. I'm not debating this with anybody, I'm just stating how I interpret it. :20:

As long as there's more pressure in the tank than the water pressure outside the tank, there's zero chance of getting water into the tank.

The 500 PSI nonsense started with the J-valve that was 300 PSI on a steel LP tank. In terms of volume that translated closely to 500 PSI in an AL (and 500 PSI springs became common in J-Valves). With the advent of the SPG, some rather unimaginative types started looking around for ways to justify their rule. A rule that was no assuming religious significance rather than rational utility. They came up with some good reasons (for certain situations) and some complete stupid ones, but you know how that sort of dictator type mind set can be.

The best explanation I ever heard came from an old timer DM down in Cayman who said something to the effect that, "Computer he bad. He be come'in up with one, me'be two, ne'ber tree huner't pound. Mess bad wit de lunch time."

 

[Alex777]

<< The 500 PSI nonsense started with the J-valve that was 300 PSI on a steel LP tank. >>

Thank you! When you think about it, the "be back on the boat with 500 psi" thing cannot possibly make sense, or all those divers using J-valves would have been getting water in their tanks on a daily basis.

<< The best explanation I ever heard came from an old timer DM down in Cayman who said something to the effect that, "Computer he bad. He be come'in up with one, me'be two, ne'ber tree huner't pound. Mess bad wit de lunch time." >>

Heh heh ... You would be surprised how many things are influenced by lunch time here. For example, the dive sites which are touted to tourists as great tend to be close to the dock, resulting in longer lunch times ...

 

[Thalassamania]

Yeah, back in the middle ages (>30 years ago) I played cricket and dominoes with the Bodden Town Yellowjackets. Are they still around?

 

[Alex777]

Cricket & dominos are still as big as ever here. I'm not sure about the Yellowjackets. I'll bet those were pretty good days, though, and not just for the diving!

NOTE to visitors: You can witness authentic Caribbean-style domino playing at My Bar at Sunset House on Sunday "evening" which, in the Caribbean, starts at 3 PM. It sounds like a cross between a university debate and a knife fight.

Cricket is played at the field near the airport, also on Sundays. It's a bit more restrained.

If Thalassamania is playing, it will be announced here.

 

[lilo]

Ok, this might be a stuip question but here it goes....is it required or recommended to do deco stops not mattering the depth you are in?

 

[Thalassamania]

I make the cutoff at 30'. Shallower no, deeper yes.

Is that arbitrary? Yes.

Is there an objective depth? Yes, 24'. But even that is arguable today.

 

[Gene_Hobbs]

<snip>...one bit of decent reading from 2004 is Deep Stops: Can Adding Half the Depth of A Safety Stop Build in Another Safety Margin (or the actual paper referenced in that article).<SNIP>

This paper should be read with the letter to the editor that followed it as well as their reply. RRR ID: 3805

The value of safety stops on VGE is best found in this thesis:
Doppler Detection of Silent Venous Gas Emboli in Non-Decompression Diving Involving Safety Stops.
Uguccioni. 1994 MS Thesis
RRR ID: 3430

Animal work on ascent rates:
Ascent rate, post-dive exercise, and decompression sickness in the rat.
Pollard et. al. Undersea Hyperb Med. 1995 Dec;22(4):367-76.
RRR ID: 2210

Reduction of decompression illness risk in pigs by use of non-linear ascent profiles.
Broome. Undersea Hyperb Med. 1996 Mar;23(1):19-26.
RRR ID:

The DAN Study on humans has not been formally written up but the results were as expected. (study here)

This was also a nice review of what people do (though a little old now):
ASCENT RATES IN RECREATIONAL SCUBA DIVES RECORDED IN PROJECT DIVE EXPLORATION.
DeNoble et. al. UHMS 1998 Meeting abstract.
RRR ID: 662

No discussion of ascent can be complete without this great workshop:
Lang, M.A. and G.H. Egstrom (eds.). 1990. Proceedings of the AAUS Biomechanics of Safe Ascents Workshop. Woods Hole, MA. 220p. RRR ID: 4241

enough for me tonight... Hope these are useful...

The 'deep stops' topic is going to be looked at in MUCH greater detail later this year, hope to see you all there.


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[Darnold9999]

Learned to dive when 60' per minute and no safety stop were the rules.

Now I do a safety stop whenever a slow swim to the surface isn't more interesting. i.e. a boat dive. Shore dive I just swim to the beach/shore and don't worry too much about timing my depth.

It is however a safety stop so I will skip it altogether if I have a good reason to. i.e. if staying down is going to be unsafe for whatever reason I will skip the stop and not sweat it at all.

Last time I skipped it we were in a high current area and the current changed direction just before we exited the channel - staying down would have blown us into the middle of a high current 9 knots plus narrow channel with lots of boat traffic. Getting out of the water was a priority so skip the stop. First dive of the day, 40 minutes or so at 70 feet as I recall. We were near the end of the dive so had already come up to 40 ft or so.

It does bother me that some divers will put themselves at risk just to make sure that they do the safety stop because its a rule.