3 or 5 minute Safety Stop?

[Kokeldil]

Finally, I'm wondering if doing several stops or pauses would be an even better way to perform ascents.
What's the safest way to perform ascents and what exactly are we trying to do? Prevent silent bubbles, prevent DCS, prevent what?
How do you ascend? Are you considering making changes?

Each and every of my dives is ascend, which means I hit the bottom quick (be it at 100 or 30 ft.) and then "start the dive" = ascend. This is exactly how vaguely 90% of my dive profiles look like. As said here before already the proper ascend prevents DCS - that´s about it. I for one am one of those who do safety stops in a manner of "sit down" somewhere at either 10 or 15 ft. and stare at the computer for the next 3 - 5 minutes, but the safety stop is part of my dive and on many dive sites it´s been the most enjoyable and most relaxing time of the dive for a number of reasons:

* psychological: any possible "what if"-thoughts which may occur at certain depth and/or under the influence of nitrogen narcosis won´t ever hit you during "safety stop", because you´re technically back on the surface already and all it takes is one or two fin kicks to stick your head out of the water again. that also means you can really let go and purely enjoy (not saying I don´t enjoy deep dives, but adrenaline level for sure is different down there)
* physical: the light and the colors are more beautiful at saftey stop depth
* murphy´s law: the biggest fish will approach right before you want to surface
* safety: well yes, just that ... mentioned a couple of times here already

I personally have set my computer to do "deep stops" but usually ignore them, as my ascend rate is far lower than what is claimed to be safe. I do not ignore "deep stops" in case I was deeper than 100ft.

I don´t do safety stops - I spend way more time (than what is required or recommended) at safety stop depth at the end of each dive anyway. No, I don´t consider making any changes.

 

[maniago]

Try yoga.

I've been told that before. In fact I've been encouraged to get my cert and teach it. But all the classes I've seen are very lady focused, and not really realistically guy body focused, as in what most guys can flex and do or more importantly not do. Besides Tai Chi is really more up my budda belly alley anyway...

 

[uncfnp]

I've been told that before. In fact I've been encouraged to get my cert and teach it. But all the classes I've seen are very lady focused, and not really realistically guy body focused, as in what most guys can flex and do or more importantly not do. Besides Tai Chi is really more up my budda belly alley anyway...

Have you tried the yoga P90x version. I don't think you could get much more "guy" focused then that.

 

[maniago]

Have you tried the yoga P90x version. I don't think you could get much more "guy" focused then that.

Hmm. Quick you tube scan of that and it does seem more like what I'd be inclined to do. Thanks for the tip!

 

[uncfnp]

That would be a decompression dive and I would be following the deco schedule presented by my PDC, adding an additional safety stop at the end, gas permitting. I wonder if those were type I or II hits? Deco diving usually presents a higher incidence of type I hits. In this thread, we are discussing NDL diving, which is far, far different. How many "undeserved hits" from NDL divers were type 1? How many "undeserved hits" from NDL divers were type II? According to DAN, they are almost all type II. If getting DCS is just a little more than statistical noise, then getting type I DCS for the recreational diver is really rare. Consequently, I'm going to dive in a manner that minimizes type II DCS even further. That for me means a two minute deep stop and a full five minute safety stop. I feel far better when I do this and that anecdotal evidence is enough for me.

Exactly, on deep dives, deep stops (beyond the deco planned ascent) and for that matter slow ascents are not recommended. The diver is still on gassing. As TSandM said faster rate on deeper end and slower rate on shallow end. For the majority of recreation divers, the "deep stop" is deep only in that it is deeper then the 20 to 15 feet of the safety stop. That means that for the vast majority of us, that extra stop is above 60 feet and that, as I understand it, the diver is off gassing at this point so in essence it could be thought of as an extra "safety stop" and not truly a deep stop. It could also be looked at, at that depth, as an aid to slowing an ascent that might be just a little too fast. I can only see deep stops within recreational limits as a win-win situation, more time above 60 and possibly a slower ascent.

Edit: by fast I mean 60 and slow at 30 for ascent rates.

NetDoc. I wonder how many of those aches, pains and minor rashes that we recreational divers get are undiagnosed Type 1?

Question. When one recommends no faster then smallest bubble, how fast do those smallest bubbles rise?

 

[The Chairman]

Exactly, on deep dives, deep stops and for that matter slow ascents are not recommended. The diver is still on gassing.

Not all tissues. In fact, after 25 minutes at depth, your neural and blood tissues are about 98% saturated at that depth. So lets do a dive to 100 ft on 32EAN_x, With a EAD of just over 80 ft, we are well within NDL. This assumes that neural fluids have @ a 5 minute half time. I've heard that it's 3-5, so this will give us some conservancy.

Time	Tension PPN2	Absorbed PPN2	Total PPN2
5	1.94	o.97	1.75
10	o.97	o.48	2,23
15	o.48	o.24	2.47
20	o.24	o,12	2.60
25	1.2	0.06	2.66

That's 3.4 times the N2 we have on the surface. Now lets go to 50 ft (1,5 atm). We will be breathing 1.7 PPN2 while our blood/neural tissues are at 2,66. That's off gassing in my book, and it's offgasing the tissues that scare me the most. Using my best guestimate (I am not going to attempt the calculus) I bet you get rid of half an atm of N2 from your blood/neural tissues before you hit your safety stop. You'll probably lose another .8 of an atm during the safety stop, bring the dissolved N2 to 1,4 or a bit less than twice your normal N2. This is skads better than doing a single 3 minute safety stop.

 

[RJP]

Exactly, on deep dives, deep stops (beyond the deco planned ascent) and for that matter slow ascents are not recommended. The diver is still on gassing. Question.

Download the trial version of V-planner and run a few tables. The output will tell you, for any dive, at what depth offgassing begins. (Based on the underlying model, of course.)

 

[TSandM]

A lot of the problems with these discussions are illustrated in just these few posts.

Definitions aren't clear -- What IS a "deep stop"?

Stops when executing deeper, staged decompression dives are different from stops executed when the entire dive is done within NDLs.

Ascents rates often aren't clearly discussed when discussing stops.

One of the biggest problems with recreational dives is the lack of control in the top ATA, especially in the top 15 feet AFTER the safety stop. Thalassamania has often stated that the safety stop was instituted to enforce some kind of ascent rate control in the shallows; one could also consider that the safety stop ensures that the fast tissues offgas to a sufficient degree during those 3 to 5 minutes (and note that 5 minutes is the half-time for the fastest compartment) that poor ascent rate control from there to the surface is less likely to be injurious.

DEEP stops, however, are quite different from the original question, regarding whether the shallow stop ought to be 3 or 5 minutes. Deep stops are posited to provide bubble growth control -- allowing elimination of nitrogen while still under sufficient ambient pressure to keep bubbles from forming, or from expanding if they have formed. Recommendation for the depth and length of deep stops are very variable. NAUI recommends, if I remember correctly, 2 minutes at half maximal depth for a recreational dive. UTD teaches one minute stops at 80% of your average bottom time ATA, which is very deep. The DAN Symposium on Technical Diving included at least one speaker who presented data suggesting that stops that deep are counterproductive; making such stops on a recreational dive are pretty obviously absurd, and really convert an ascent into a multi-level dive.

It all gets even more interesting, and frustrating, when you realize that the incidence of DCS in recreational dives done within no-deco limits is EXTREMELY low, which means you have to study a LOT of dives to see anything make a significant difference -- and those studies are expensive, and in view of the low incidence, not studies anybody is really all that interested in doing. So today, we use Doppler bubble studies as a proxy for DCS, which is a very flawed proxy, as high bubble grade and symptoms do not correlate all that well. I do believe studies are ongoing, however, in measuring bubble grades in divers using various ascent strategies, but primarily on technical dives.

For recreational dives, I think you can say that, if you stay within your no-deco limits for the model you are using (whatever it is), and you control your ascent rate, your likelihood of DCS is extremely low -- so low that no one can really tell you whether 3 or 5 minutes at 15 feet is better.

 

[BDSC]

Excellent post!

 

[ev780]

A lot of the problems with these discussions are illustrated in just these few posts.

Definitions aren't clear -- What IS a "deep stop"?

Stops when executing deeper, staged decompression dives are different from stops executed when the entire dive is done within NDLs.

Ascents rates often aren't clearly discussed when discussing stops.

One of the biggest problems with recreational dives is the lack of control in the top ATA, especially in the top 15 feet AFTER the safety stop. Thalassamania has often stated that the safety stop was instituted to enforce some kind of ascent rate control in the shallows; one could also consider that the safety stop ensures that the fast tissues offgas to a sufficient degree during those 3 to 5 minutes (and note that 5 minutes is the half-time for the fastest compartment) that poor ascent rate control from there to the surface is less likely to be injurious.

DEEP stops, however, are quite different from the original question, regarding whether the shallow stop ought to be 3 or 5 minutes. Deep stops are posited to provide bubble growth control -- allowing elimination of nitrogen while still under sufficient ambient pressure to keep bubbles from forming, or from expanding if they have formed. Recommendation for the depth and length of deep stops are very variable. NAUI recommends, if I remember correctly, 2 minutes at half maximal depth for a recreational dive. UTD teaches one minute stops at 80% of your average bottom time ATA, which is very deep. The DAN Symposium on Technical Diving included at least one speaker who presented data suggesting that stops that deep are counterproductive; making such stops on a recreational dive are pretty obviously absurd, and really convert an ascent into a multi-level dive.

It all gets even more interesting, and frustrating, when you realize that the incidence of DCS in recreational dives done within no-deco limits is EXTREMELY low, which means you have to study a LOT of dives to see anything make a significant difference -- and those studies are expensive, and in view of the low incidence, not studies anybody is really all that interested in doing. So today, we use Doppler bubble studies as a proxy for DCS, which is a very flawed proxy, as high bubble grade and symptoms do not correlate all that well. I do believe studies are ongoing, however, in measuring bubble grades in divers using various ascent strategies, but primarily on technical dives.

For recreational dives, I think you can say that, if you stay within your no-deco limits for the model you are using (whatever it is), and you control your ascent rate, your likelihood of DCS is extremely low -- so low that no one can really tell you whether 3 or 5 minutes at 15 feet is better.

Damn data!! Screwing with everyone's misconceptions. I have never seen so much worry in people over a non-existent injury/death rate in recreational diving. Maybe the baby crib thing was worse.