Deco + safety stops?

[grassybreakfast]

I don't believe in "safety stops" for deco dives. I don't know why you would need it. If you think that your planned deco stops were not enough and you now need to do a "safety stop" after you clear deco then you have piss poor planning and you should not have even started the dive.

I say plan your dive and dive your plan.

Pick what you deem an acceptable GF, plan your dive on that GF, when you computer says deco clear then you can safety surface. If you feel to you need to do a "safety stop" once you clear deco then as I mentioned be for you have piss poor planning.

Now I will say there is difference between a "safety stop" and and emergency contingency plan. So yes if you feel some twinging or something odd in a joint or you just don't feel right about the quality of your decompression then yeah listen to your body and spend 30 more min at 6m on O2 (or however much time you need)

Yeah that's totally reasonable, but why are NDL dives different? You have also picked an acceptable GF, dived on that GF, and didn't exceed NDL, so why not just surface? Or do you also not do safety stops on NDL dives?

 

[grassybreakfast]

FWIW, I believe this is related to the time-to-fly. On an NDL dive, we would feel very safe exiting the water with a GF99 of 65, right? At first glance, one might suppose that you just need to wait long enough so your GF99 at cabin pressure was below 65. Unfortunately, a study by Duke Univ. showed you would almost certainly get bent. The fact is we bubble, and it's quite easy to catch some of them with a safety stop.

Plus, it's nice to wait at depth for the ladder to clear rather than in rough surface chop.

It is really interesting how much we still don't understand about deco. Really curious what deco theory will be like 10 or 20 years from now.

 

[DiveLikeAMuppet]

Safety stop is a short deco stop, but the name was too scary to include in recreational dive manuals so it got called “safety” stop. If you finished your deco, why do more deco?

If you do plan to dive from a boat in the UK, explore a twinset, you will be happier on dive lifts.

For ADP, make sure you train with a good instructor. There is a reason for the stereotype of sea-horsy BSAC techie divers (with hammers and crowbars). Some of the clubs are great, some lack standards and knowledge especially around technical training.

 

[boulderjohn]

Yeah that's totally reasonable, but why are NDL dives different? You have also picked an acceptable GF, dived on that GF, and didn't exceed NDL, so why not just surface? Or do you also not do safety stops on NDL dives?

I wrote before that I use SurfGF as a guide for safety stops. Here is more on that process.

I use a higher GF high setting for NDL dives than I do for tech dives. There is a potentially silly reason for it, which I will explain below. As a result, when I reach safety stop depth, I may have a higher SurfGF than I am comfortable with for surfacing. I wait until it drops to a number I like. That is a safety stop. It might be less than 3 minutes. It might be more.

I used to do NDL dives with the same settings as tech dives. The problem was it gave me a very short NDL, and I was going into deco well before the ones with the typical dive computers. I knew that if I had taken a few seconds to change my GFs, I would still be within NDLs, so I just let it go a few minutes into deco. I would usually finish my deco before they had finished their safety stops. No problem, right?

I made the mistake of mentioning this on ScubaBoard, and someone made a big deal about it, calling for me to be banned for advocating people doing decompression dives without training or equipment. To get to the end of the story, I change my GFs for NDL dives so that no one gets excited about me going into deco on an NDL dive. You never know when some dimwit is going to have a hissy fit about it.

 

[Manatee Diver]

don't believe in "safety stops" for deco dives. I don't know why you would need it. If you think that your planned deco stops were not enough and you now need to do a "safety stop" after you clear deco then you have piss poor planning and you should not have even started the dive.

I say plan your dive and dive your plan.

Pick what you deem an acceptable GF, plan your dive on that GF, when you computer says deco clear then you can safety surface. If you feel to you need to do a "safety stop" once you clear deco then as I mentioned be for you have piss poor planning.

I think you are confusing needing a safety stop and simply adding it as additional padding into the safe zone. Sure I should be able to immediately exit the water when my I clear deco but unless there is a pressing need, oxygen is cheap and extending my final stop puts me further away from the line. So if for whatever reason the biological factors involved in DCS are stacked against me, I am still unlikely to get bent as I exited well away from the planned line.

 

[grassybreakfast]

I wrote before that I use SurfGF as a guide for safety stops. Here is more on that process.

I use a higher GF high setting for NDL dives than I do for tech dives. There is a potentially silly reason for it, which I will explain below. As a result, when I reach safety stop depth, I may have a higher SurfGF than I am comfortable with for surfacing. I wait until it drops to a number I like. That is a safety stop. It might be less than 3 minutes. It might be more.

I used to do NDL dives with the same settings as tech dives. The problem was it gave me a very short NDL limit, and I was going into deco well before the ones with the typical dive computers. I knew that if I had taken a few seconds to change my GFs, I would still be within NDLs, so I just let it go into a few minutes into deco. I would usually finish my deco before they had finished their safety stops. No problem, tight?

I made the mistake of mentioning this on ScubaBoard, and someone made a big deal about it, calling for me to be banned for advocating people doing decompression dives without training or equipment. To get to the end of the story, I change my GFs for NDL dives so that no one gets excited about me going into deco on an NDL dive. You never know when some dimwit is going to have a hissy fit about it.

Yeah that makes sense and I suspected that to be the case, with many recreational shops/boats not "allowing deco". I really appreciate BSAC introducing deco early in the curriculum, and I feel it leads to a more healthy attitude towards deco vs treating it as a black and white line. But it does require more personal responsibility.

 

[Underwater Tourist]

Somebody on the forum posted this link about SurfGF that might be helpful for you:

Shearwater Dive Computer Settings: Become A GF Power User!

An illustrated guide to getting the best out of your Shearwater dive computer settings. Don't be intimidated by the advanced display options!

scubatechphilippines.com

 

[Alex Ouroboros]

Hello!

I am a rec diver certified for back gas deco (I am aware that some agencies consider any deco diving to be tech, but not BSAC!) but haven't actually done it except simulated deco during training. I have avoided it because I personally consider significant deco obligation without redundant gas to be outside of my risk profile.

However, now that I am getting into redundant gas (haven't decided between sidemount or twinset and will probably do training for both to decide), I am looking to diving deeper/longer with planned deco.

One thing I find intriguing is how people who do deco think about safety stops. It seems like the most popular school of thought is if you are doing deco, you are planning your own safety margin with GF (or equivalent), and so there is no need for safety stops. That's fine, but then do you do safety stop on a NDL dive? If yes, isn't there a bit of a disconnect in safety margin since completing deco puts you at GF high, which is exactly where you would be if you were just inside NDL? Or do you do safety stop in addition to deco? Or do you also not do a safety stop on NDL dives?

It seems like the most scientifically-based way to manage safety margin is to either set GF high to what you deem acceptable, and aim for a lower SurfGF if possible, or GF high to what you aim for, but be happy to surface earlier if necessary when SurfGF gets to what you deem acceptable.

What strategy do people use?

I do the deco as per computer / slates (yes I am that old) and at each stop I’m in no rush to ascend the next stop, always being in touch with how my body is feeling,
In my experience after long deco obligations (2-4hrs) I’m always very cautious of being in a rush to leave the shallowest stop and head to surface so I sometimes pad that out by 10-15% on the basis that only a few minutes can make a big difference to how good you feel when you get out never mind goading mr bendy or fizzy lizzy, and I come up from 6m in about 2-3 min)
Basically in your position I’d do the safety stop also as an additional precaution if safe to do so, at 6m depth your hardly burning any gas and after a dive for an hour plus (am guessing here) what’s a few minutes going to cost you?
(Extra time on the shallow deco I swear makes me feel less lethargic and generally better,,, that tiredness you sometimes feel after a dive is much to blame on the body’s amount of residual nitrogen,,, in effect your still decompressing for the next day or so ,,,, hence no dive n fly, think about the physics )

 

[runsongas]

once it is planned decompression diving, its not so much adding a safety stop as padding the deco for a surf GF you are happy with

 

[boulderjohn]

In my experience after long deco obligations (2-4hrs) I’m always very cautious of being in a rush to leave the shallowest stop and head to surface so I sometimes pad that out by 10-15% on the basis that only a few minutes can make a big difference to how good you feel when you get out never mind goading mr bendy or fizzy lizzy, and I come up from 6m in about 2-3 min)

Whether or not this is a good idea is a matter of debate. There is a big difference between dives with required decompression and NDL dives, and this issue is at the heart of that difference.

On an NDL dive, if you begin the ascent within NDLs, it does not seem to matter how long you take on that ascent, as long as you do not exceed NDLs along the way. If you leave 100 feet within NDLs, you should be able to go directly to the surface (at a safe rate of speed), do a 3 minute safety stop, do a 5 minute safety stop, check out a shallower portion of the reef for 15 minutes--whatever. Extending time at safety stop depth is beneficial, whether needed or not.

If you have required decompression, it is quite the opposite. If you extend deeper decompression stops, you have to extend the shallowest stops to compensate. While you are extending those deeper stops, your slower tissues are on-gassing, and you will need to give them time to off-gas during the shallow stops.

It is very much like the change in thinking on deep stops. Twenty years ago, people thought doing stops much deeper than were traditionally done was good practice, but that thinking has largely gone away as research shows that the added nitrogen loading at depth was not a benefit.