safety stop question

Ok, so this popped in my head the other day. Back when i took my AOW our instructor had us do safety stops where what ever depth you were at divide by half and then do 1 minute stops from there and every 10 feet up. So if we dove down to 80feet our first stop would be at 40ft for a minute, then 30ft for a minute, 20ft for a minute and lastly 10ft for a minute and then surface.

Is there a benefit to doing it this way over ascending from 80ft, or whatever depth you were at, to 15ft for 3-5 minutes? I didnt think to ask why back when i took the course.

It is difficult to prove a benefit, simply because the incidence of DCS in dives conducted within no-deco limits is so low.

There is theoretical benefit, if you consider bubble models of decompression. Assuming we all start with some degree of microbubbles, going very shallow before stopping allows the maximum amount of bubble expansion, and gas that's trapped in bubbles is much more difficult to offgas than gas dissolved in fluid. In addition, larger bubbles are likely to cause more problems than smaller ones, in terms of interruptions of capillary blood flow, and inciting of any immune response which may be involved in DCS. But this is really all theory.

As a practical benefit, disciplining your ascent in this way gives you constant practice in pinpoint buoyancy control all through the shallow water, which is never a bad thing. And it tends to keep divers together, as the frequent stops allow regrouping.

And on a purely anecdotal level, I know I feel much better when I execute stepped ascents.

Ok, Although TSandM may be correct, It seemed a bit more like showing off how much knowledge they had as oppose to answering the dang question. In my opinion, all those stops are beneficial but not really necessary or practical for recreational diving. I would recommend doing the half way stop, and then your safety stop.

Like TSandM said, it's all a theoretical benefit when comparing one long safety stop VS short but multiple safety stops.

I'm not a fan of holding at 10ft though. I like to keep my last stop at 15ft, at the very least. The most safety stops I've ever done in a dive was 3, totaling 7mins. The total ascent time when I was following that plan was usually around 12-15mins from 80ft. So in a way I was following your instructor's advice.

Holding those last 3 mins in 15ft of water with waves and current is no bueno, though. I wouldn't want to go through that at 10ft.

I think following your instructors advice to the letter would benefit more to a fast ascender than to one who did a very slow gradual ascent to their safety stop(s).

tylerinflorida:

Ok, Although TSandM may be correct, It seemed a bit more like showing off how much knowledge they had

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TSandM is a "she", not a "they". I believe TSandM were three cats she and Peter used to have.

fncrow:

Ok, so this popped in my head the other day. Back when i took my AOW our instructor had us do safety stops where what ever depth you were at divide by half and then do 1 minute stops from there and every 10 feet up. So if we dove down to 80feet our first stop would be at 40ft for a minute, then 30ft for a minute, 20ft for a minute and lastly 10ft for a minute and then surface.

Is there a benefit to doing it this way over ascending from 80ft, or whatever depth you were at, to 15ft for 3-5 minutes? I didnt think to ask why back when i took the course.

Click to expand...

Years before anybody was really talking about deep stops in recreational diving, I made up my own little rules when I was a Divemaster.

What I demanded was that everyone stop at 30 feet, check their air and show me their gage.

I never disclosed the real purpose, but it was EXTREMELY effective in preventing uncontrolled ascents. I taught it to some other DM's and at first they thought it was stupid, but after they tried it a few times they also benefited from much more serene ascents.... no more chasing customers or trying to dart out and snatch the fin tip of a buoyant clown as he floats past the group.

I found that if I could get the people to try to totally STOP their ascent at 30 feet, many of them would be successful, but a good percentage would not. HOWEVER, since they were really TRYING to stop at 30 feet, they would almost always get their sXXX together by the time they floated up to 15 feet. Very few would totally lose it and blow all the way to the surface. Demanding a stop around 30 feet was EXTREMELY effective in getting "tourist" type divers from endangering me and themselves via run away ascents. So there is a VERY practical reason to direct people to STOP well below 10-15 feet.

Now we have more information about the idea of deep stops, I've noticed big improvements in how I feel when doing a deep stop. On no-deco dives to even 130, I will stop at around 50 feet, chill for a minute or two.. generally wait there until my heart rate is really relaxed and then slowly move on up toward 20 feet, where I will do another short stop.

I don't follow 1 minute at each 10 feet, but that is perfectly fine way to do an ascent; I just come up real slow to 20 feet over a period of maybe 2 minutes (which is of course close to 1 minute stop at each 10 ft increment). When diving really hard, doing 4-5-6 dives per day to or past the recreational (no-deco) limits, I quite often got "pole spear elbow" (I was spearfishing). A pretty painful condition in the one elbow that lasted for a while on the boat, often for an hour.

After I started doing the deep stops, no more pole spear elbow.. the difference was pretty dramatic.

There is a body of thought that recommends what you were told. There is a body of thought that thinks they are wrong. What you are seeing is the fact that no one really knows for sure.

DAN has done some studies on this. If you really want to dig into it, you can search around their site. Sadly, you will find nothing really definitive. I was taught both ways at different times in my career. In No decompression diving, I have reached the point where I don't think it matters a whole lot and do whatever everyone else with me wants to do.

Yea i figured it wouldn't really mater if you are staying within NDLs. I also figured since my AOW instructor was also a tech diver/instructor that maybe it stemmed from that mindset and having to do multiple deco stops or something.

We have been training our divers for a decade to do:

* a 40' stop ( less than a minute or longer depending on gas supply and marine life )

* then a 25' stop for 1 -3 minutes ( or more again depending on gas supply and marine life encounters )

* then the usual 3 - 5 mins at 15' ( or more again depending on gas supply and marine life encounters )

Hopefully, the sharks will show up at 40', the dolphins at 25 and the manta rays at 15'!

Now, we use the Scubapro Galileo Sol which has the Profile-Depenent Intermediate Stop ( PDIS ).

It tells you when and how long to do the intermediate ( deep ) stop. Also, it takes into account the accumulated nitrogen from previous dives.

Of course, you still want to do safety stops.

Dr. Bennet did write an article a couple of years ago and they did see a benefit in deeper safety stops. You will have to do a little digging around and if memory serves it was 1/2 the deepest part of the dive, but for 3 minutes and then proceed to 15fsw for a 1-2 minute stop. Of course following a safe ascent rate of 30 fpm. NAUI does ascribe to this calling it the rule of halves