3 or 5 minute Safety Stop?

[GrumpyOldGuy]

Here is how I look at it. Do I have enough gas to safely do a 5 minute stop? Do I have any other pressing reason to get out of the water? Am I here to dive? A safety stop is still diving, and sometimes the best diver mistakes are made at the safety stop, giving you something to chuckle about. Often, the manta rays and whale sharks swim by on the safety stop. There is no good reason not to stretch it out.

BINGO, WE HAVE A WINNER!

I never understand people who rush to finish a dive. You paid for the dive so you might was well stretch it out until you run low on gas or hit the dive boat window. I am constantly amazed about the different view at 15' under the boat rather than being 3' off the reef. Everything from seals to reef fish looking for a handout from the boat. Even shore diving, there is an amazing amount of sea life in the top 15'. Its like "free" dive time or a friend offering to but you a beer, why turn it down.

 

[RJP]

If you have ever dove with someone who is using a suunto computer believe me, it doesn't like those deep stops. It will continue to rack up deco until you wind up doing a 15 minute deco stop at 15ft deep on a dive where you went with someone else who had one after only a 60ft dive and less than an hour.

Depends on the computer. The Vytec DS (DS=Deep Stop) can be set for deep stops or no deep stops. Mine does NOT continue to rack up deco when set for deep stops.

 

[supergaijin]

Almost none of my dives involve a direct ascent to the surface. When it's time to turn back I head for 30' and slowly cruise up to 15'. I putz around that depth heading back to my exit point and eventually the bottom takes me up to the surface. I probably spend about 10 minutes at 15' and another 5-10 minutes to reach surface. Doesn't work from a boat but I am almost always diving from shore. I wounder if I'm doing anyting wrong.

Nothing wrong there as you're not 'deep' at 30'. A dive to 4ata for example to 'no deco limit', then trying to eke out every minute of 'no deco' on ascent is thought by some to be riskier than a dive to the same depth, and then a fairly brisk ascent to around 2ata, then a longer spell there before ascending for a safety stop.

That said, the vast majority of computers are conservative. Divers don't drop like flies from 'riding the computer'. Plenty of these kind of multi-level dives are made every day without incident. At the same time, all recreational agencies tell you to dive conservatively and not dive to the deco limits.

IMO it is safer to dive to the 4ata 'limit' and then ascend relatively shallow, compared to diving to the 4ata limit, ascending and diving to the 3.5ata limit, then the 3ata limit etc. The modern dive computer calculates for this. Many divers do not have the gas required to do this profile anyway, but a small point can be made about different profiles and assumed risk. At least one study has shown that very slow ascents increase 'silent bubbles' compared to a faster ascent to the safety stop.

 

[uncfnp]

What year is your computer or model? I have 2 that are > 7 years old and a friend of mine has a newer model. I don't recall that option. I surmise we were diving approximately the same profile, she maybe even shallower than I. Our first year in Cozumel, I was using the predator and as we ascended mine compensated for the ascension as hers continued to obligate her to more deco until we hit the safety stop zone. We would wind up hanging at 15ft for several minutes longer to clear her ceiling. I am not an expert algorithmist but there are also warnings in the manuals on certain computers ( I own 4 different ones) that say they are only for recreation, not technical diving as the predator is designed for.
...

I don't own one, I have an Oceanic, but I have been looking at the Sunnto for its conservatism and the deep stop option. I know most of the newest models (not the Zoop) offer it but don't recall the exact models, D6, D9 and Vyper I believe. They call it the Deep Stop RBGM algorithm. I have been unable to find out how it is incorporated into recreational dives and if it changes the SS.

 

[Paulmal]

Most of the divers I do deco dives with add a couple extra minutes of O2, after we clear our last stop. I see no harm in doing similar on a rec dive.

 

[The Chairman]

I was listening to a DAN presentation at the History of Diving Museum (MM 83, Bayside), and the one thing that stuck out to me, was they could accurately depict what kind of diver you are depending on the type of DCS hit you got. If you got a type I, then you were a commercial diver. If you got a type II (neurological hit) then you were a recreational diver. Now, getting bent is pretty rare. So much so, that the presenter referred to it as slightly above statistical noise. But if you do get DCS, then they can categorize your diving with like a 98% accuracy. That's a wow in my book.

Later on in his presentation, he casually brought up that the half time for neural fluid was about the same for blood, @ 5 minutes. Now, if you think about it, it only takes about five half times to approach saturation (98.4%). Do the math and that's only about 25 minutes at depth to bring your neural fluids to 98.4% of being saturated at that depth. Doing a five minute half stop will reduce that excess by 50%. That only makes sense to me, so I just do a five minute safety stop. IOW, I'm going to ameliorate the already low percentage of getting bent by addressing the way I'm probably going to get bent in the unlikely event that I do.

BTW, the people who always seem to be overly tired after their dive, never seem to have done a deep stop or a full five minutes at their safety stop.

 

[denisegg]

Most of the divers I do deco dives with add a couple extra minutes of O2, after we clear our last stop. I see no harm in doing similar on a rec dive.

Ok...so...a lot of divers don't have 02 as an option as deco divers do (unless they wind up on the boat with it) We can argue for days..but the more you learn..study all the books about air, gas mixes, trimix, algorithms, the less you know (or at least that is the way I felt). When I took advanced nitrox/deco..you realize you are in a world all your own. And ultimately, who decides the fate?

 

[vladimir]

What year is your computer or model? I have 2 that are > 7 years old and a friend of mine has a newer model. I don't recall that option.

'Deep Stops' are a bit fashionable now and Suunto has only added them to certain computers quite recently.

The Suunto D9 first came out in 2004, if I recall correctly. I have had mine for over 8 years and it has the option to use deep stops.

 

[Atom]

If you have ever dove with someone who is using a suunto computer believe me, it doesn't like those deep stops. It will continue to rack up deco until you wind up doing a 15 minute deco stop at 15ft deep on a dive where you went with someone else who had one after only a 60ft dive and less than an hour.

This depends on the model. And I'm reasonably sure all the new models don't do that anymore.

I have a Vyper Air and even though it is conservative, if you send it into deco it can clear while you're ascending if your ascent is slow and you only have a few minutes. It also has deep stops (optional), but I'm not convinced it does anything more than show you a timer at the stop depth, it also doesn't seem to mind at all if you blow through the deep stop.

I certainly wouldn't use it as a deco computer, but on the new models if it goes into deco, don't freak out, just start a slow ascent and most likely it'll clear before you reach the ceiling it shows you. Then take some time to think about how you got into that situation (not monitoring your remaining bottom time) and how to avoid the problem on your next dives.

 

[lowviz]

...//... They call it the Deep Stop RBGM algorithm. ...//...

The RGBM algorithm is a computational nightmare. This http://www.scuba-doc.com/rgbmim.pdf is one of the more readable documents that comes close to answering (in words) how RGBM is incorporated into recreational diving. You may still need a shovel to get through some parts of it though.

BTW, life will be much simpler if you can talk your dive buddy into getting the same DC. Buhlman and RGBM pretty much part company at the first stop.