3 or 5 minute Safety Stop?

Please register or login

Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

Benefits of registering include

  • Ability to post and comment on topics and discussions.
  • A Free photo gallery to share your dive photos with the world.
  • You can make this box go away

Joining is quick and easy. Log in or Register now!

When reading articles on different theories, just remember that they all agree on one thing: at the moment the causal nexus is poorly understood and so beyond a few definitive baselines (longer and deeper = more gas absorption for example) there are very few definite answers in terms of ascent profile.

My point exactly...Don't push it to the limit. Penetrate, then, slow, very slow and have plenty of gas left to ascend at a descent rate.
 
'Deep Stops' are a bit fashionable now and Suunto has only added them to certain computers quite recently.

Finally, I'm wondering if doing several stops or pauses would be an even better way to perform ascents.

For my typical 'deep' dive to around 4ata, a deep-stop would not do much to decrease the already low chance of DCS. From what I know (reading about Pyle and Deco for Divers), to benefit from a deep-stop, you first have to have gone deep. Deep in this context is beyond the typical recreational dive limit of 5ata.

Safety stops have been shown to decrease silent bubbles. A longer SS of 5mins will mean less silent bubbles than after a 3min stop. That is a good thing and something I try to implement whenever feasible, and what I train AOW divers to do after 'deep' dives.

What's the safest way to perform ascents and what exactly are we trying to do? Prevent silent bubbles, prevent DCS, prevent what?

A certain amount of supersaturation is required to off-gas. Your body can tolerate a Maximum Value of supersaturation before an unnacceptable amount/size of bubbles form. Getting to the limit (but not over) means the maximum amount of off-gassing at a safe rate. A slow ascent (<1ata/min) does not do this, so a faster initial ascent is seen as 'good' and then a very slow final ascent in the shallows. This is typical of a 'bend and mend' profile with Bulhmann-based dive computers.

Ascents should prevent DCS first and foremost.

Silent bubbles are thought to contribute to DCS and Suunto models account for this with shorter overall bottom times, penalties for various infractions etc. Some divers bemoan the shorter bottom times, however IMO, conservatism in diving is a good thing.
 
I am not really sure what the question is here, considering the comments so far. However, I assume that it is: Is a 5 minute safety stop better than a 3 minute safety stop? Yes. In Australia the recommended stop changed from 3 to 5 minutes at least 20 years ago but I note that in the US this does not seem to have been adopted. It is no more onerous to do 5 mins than 3 mins and takes hardly any more air. Do 5 minutes!!!
 
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.
 
I just got back from a trip to Bonaire where we did several boat dives which I know is not what Bonaire is known for. What is interesting is how the DM's planned the dive. We were on either air or nitrox depending on your skill level. We started the dive on the wall by descending as deep as you would like to go, from about 60ft to 110ft, some went deeper. We were asked to turn at either 30 minutes or 1500 psi and then we began to ascend up the wall and finish the last several minutes of the dive at 15 to 20ft. By the time the max time of one hour was achieved you had completed a safety stop and then some.
I was not crazy about the 1500 psi turn pressure because I have gotten use to diving 1/3rds and thought people should be turning at 2000. But by following the general pattern of the dives and turning at their 30 minute limit I was still getting back on the boat with about 1/2 of my gas. I just can't envision that rule of getting back on a boat with only 800 psi anymore. I want about 1200 to 1300 psi on the boat after a one hour dive, no matter what the depth. Of course toward the end to do that I had to quit playing out at depths beyond 90ft the first half of the dive.
My point is, a gradual slow ascent while you are still enjoying the view but by planning this strategy ahead of time made for some pretty awesome dives with several minutes of safety stop zone diving while still completely enjoying the whole experience.
What is the golden rule after all, planning. :D

---------- Post added July 5th, 2013 at 07:25 PM ----------



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.

Technically that is not thirds. That is a 1/3 of the tank assuming a 3000 PSI tank.

Thirds is actually your available gas supply and leaving 300-500psi, depending on the operations desire, as not your gas unless an extreme emergency. So thirds would be 3000 - say 400 (splitting the difference) = 2600/3. So 866 for the descent, 866 for the swim, and 866 in reserve. Personally if I knew my buddy I'd be ok with rounding up to 900. If it's an insta buddy I might change that to 800.(now if you add that to the reserve you do come up with close to what you want to have left.)

Conditions also play a role. Bonaire - 900 would be fine. Great Lakes in 40 degree water I might adjust down to 750 for a single tank.

Unless it's your tank and you are ok draining it completely.
 
For me, 3 minutes is mandatory. Depending on my remaining gas and dove profile I'll stay longer. I like to hang out at that depth bc I see some there that I don't see at depth... jelly fish, dolphins, etc... so I'll off gas longer if conditions allow. It's based off of Bob's Theory.
 
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.
 
I am not really sure what the question is here, considering the comments so far. However, I assume that it is: Is a 5 minute safety stop better than a 3 minute safety stop? Yes. In Australia the recommended stop changed from 3 to 5 minutes at least 20 years ago but I note that in the US this does not seem to have been adopted. It is no more onerous to do 5 mins than 3 mins and takes hardly any more air. Do 5 minutes!!!

If you look back, the OP asked several interesting questions. Your choice which to answer, any or all.
 
I spent a lot of time studying the technical aspects of the body's gas absorption at depth, impact of dive depth and time, profile variations, and ascent rates. When all is said and done, the following represent what every diver needs to know:
Ascend slowly from every dive. AND, ascend slowly during depth changes during a dive. Too many divers forget this aspect of a dive profile. They think of ascent rates only as applicable to the last ascent to the surface, and they are wrong. Slow means 30 feet per minute OR slower.
Safety stops are always a good idea, but not to be confused with mandatory deco stops. In recreational diving, safety stops are just that, to enhance safety and decrease risk. Whether 3 minutes or 5 minutes, at 15 feet or 20 feet, they are a good thing. They also present an opportunity for focus on and practice of buoyancy control, something that is useful to every diver.
Beyond the foregoing, I leave theory in the physics books and classroom and prefer to just drill these safe diving practices into students and divers by offering them repeatedly, emphatically, and as not optional. I haven't lost a student or diver yet.
DivemasterDennis
 
https://www.shearwater.com/products/perdix-ai/

Back
Top Bottom