PADI Deep Diver course 12-metre safety/decompression/"long" stop

[Chris Richardson]

I am soon to be doing my PADI Deep Diver certification to go down to 40-metres deep. The training manual says that a 12-metre safety/decompression/"long" stop for 1 to 3 minutes is sometimes done in addition to the 3 minute safety stop @ 5-metres. Up until reading the deep diver course book l had never been aware of this stop: is it generally done only for dives deeper than 30-metres or is it an optional stop? ("better safe than sorry"). Does the use of a dive computer possibly factor this stop out with a "slower than 18-metre/minute ascent rate" therefore nullifying its requirement? Thanks.

 

[Graeme Fraser]

PADI Deep Spec is strictly within the NDL (no decompression limit), so you are technically able ascend directly to the surface if you remain within these limits and at a safe ascent rate. However, although there is no mandatory stop, it is strongly advised (and required during the course) to carry out a minimum 3 minute safety stop at 5 metres.

The reference to a 12 metre stop may refer to your computer which may have a 'deep stop' option. Some do, some don't, and there is plenty of debate about their validity. Make sure you know if your dive computer has this activated in the settings and discuss with your Instructor so he / she knows beforehand.

With regards to the maximum ascent rate, the majority of dive computers stipulate 10mpm rather than 18, but again this should be discussed during the dive brief.

The key thing is to be familiar with your computer settings and layout, thus not surprised or confused by any information displayed during the dive.

 

[wstorms]

This is a tricky subject. What you referring to is quite often called a deep stop. This is a bit vague, since the term "deep stop" is mostly used with tec diving, and is not as applicable within recreational limits.

Also, in the last few years the usage of deep stops within technical diving is topic of much debate. The basic forum is no place to go into that, but you can find plenty of discussion in the technical forum. For here, let's keep it basic.

PADI no longer requires (but still allows) deep stops (per 2016 Q4 training bulletin) with tec dives, and leaves it to the dive team to choose the ascent strategy (and therefor to use deepstops or not). My expectation is that this will be adjusted in the deep specialty as well, but things like that take time (reprint books etc).
This is really something to discuss with your instructor. It is a really good topic and might lead to some lengthy discussion on tissue loading, DCS and safe pracitces.

One additional thing to consider; if you are coming back up from 40 meter it is a good idea to take a bit of time to stabilize before doing the last bit of an ascent. Better to take 30 seconds at 12 meter to properly control your buoyancy, than to loose control and shoot trough your safetystop.

 

[ScubaWithTurk]

I am soon to be doing my PADI Deep Diver certification to go down to 40-metres deep. The training manual says that a 12-metre safety/decompression/"long" stop for 1 to 3 minutes is sometimes done in addition to the 3 minute safety stop @ 5-metres. Up until reading the deep diver course book l had never been aware of this stop: is it generally done only for dives deeper than 30-metres or is it an optional stop? ("better safe than sorry"). Does the use of a dive computer possibly factor this stop out with a "slower than 18-metre/minute ascent rate" therefore nullifying its requirement? Thanks.

The 12 meter stop is not in the instructor manual for the course. It does discuss the old Navy omitted decompression procedure of descending back down to 12 meters but this is no longer recommend.

PADI Deep Spec is strictly within the NDL (no decompression limit), so you are technically able ascend directly to the surface if you remain within these limits and at a safe ascent rate.

While the course is for NDL, it does go into emergency decompression procedures and how to handle those. It also states that a diver "must do a safety stop if the dive is 30 meters or deeper"

 

[boulderjohn]

The 12 meter stop is not in the instructor manual for the course. It does discuss the old Navy omitted decompression procedure of descending back down to 12 meters but this is no longer recommend.

...which is why I had never heard of this until I saw this thread, even though I have certified a fair number of people in this specialty. What follows is some speculation coupled with recent research I have done.

When the course was written, deep stops were all the rage. many people were swearing by them, even though there was very little research to support it. There was, however, some research, some of which has since fallen out of favor. At about that time, NAUI made deep stops on recreational dives part of its instruction, and it is still part of NAUI's instruction.

Previous posters have noted that the love affair of deep stops in technical diving is clearly over. So what about deep stops on recreational dives? Well, it is complicated.

My research on recreational deep stops has made it clear to me that although all dives require decompression, there is a difference between NDL dives and decompression dives, with a gray area of transition at the limits of NDL dives and decompression dives requiring minimum decompression. Think about it this way. If you go into decompression and begin an ascent, a dive computer will penalize you for ascending too slowly, forcing you to do longer and deeper decompression stops. If you do not go into decompression and ascend slowly, that same computer will reward you by giving you more NDL time, usually without changing a safety stop requirement. You could potentially be near NDL at depth and then do a 20 minute extension of your dive at a shallower depth without a problem. You will only be penalized if your slow ascent exceeds NDL limits.

There is still very little research on deep stops in recreational diving. I was planning on writing an article about current thinking on the topic, but after researching, I decided I did not have enough of an opinion to write it. In contrast, I have firm opinions on deep stops in decompression diving.

Today, NAUI remains the only agency I know of that truly endorses deep stops on recreational dives. DAN Europe endorses them, but DAN America does not.

 

[tursiops]

I was planning on writing an article about current thinking on the topic, but after researching, I decided I did not have enough of an opinion to write it.

?? Cannot an article be factual rather than opinionated?

 

[boulderjohn]

?? Cannot an article be factual rather than opinionated?

The article would have been a few sentences long, saying pretty much what I wrote above.

 

[100days-a-year]

I would follow my computer personally.

 

[wnissen]

I am soon to be doing my PADI Deep Diver certification to go down to 40-metres deep. The training manual says that a 12-metre safety/decompression/"long" stop for 1 to 3 minutes is sometimes done in addition to the 3 minute safety stop @ 5-metres. Up until reading the deep diver course book l had never been aware of this stop: is it generally done only for dives deeper than 30-metres or is it an optional stop? ("better safe than sorry"). Does the use of a dive computer possibly factor this stop out with a "slower than 18-metre/minute ascent rate" therefore nullifying its requirement? Thanks.

I was very surprised to see that my Aqualung i550 included a deep stop that was turned on by default. On dives deeper than 24m / 80ft, it turns on a 2 minute stop at half the maximum depth. There is no penalty for skipping it, but it's disabled if you go into decompression or oxygen alarm state, so it's clearly only intended for deeper NDL dives.

 

[NAM001]

what kind of gas are you going to be using. deep on air would make sense for a stop in that region I guess but not if you are using trimix. Also could it be an issue with the bottom time of the dove