BSAC and FFESSM depth limit on recreational diver

[nohappy]

I found that BSAC's depth limit is 50m, and FFESSM's limit is 60m. (Compressed air)
Which leads me to two questions:

1. It seems that they believe it is ok to dive below 40m despite of nitrogen narcosis after training. What's the training that could make diver handle nitrogen narcosis?

2. Since NDL below 40m should be less than 10min, do they learn how to plan deco dive in their recreational diving course?

 

[Gareth J]

I found that BSAC's depth limit is 50m, and FFESSM's limit is 60m. (Compressed air)
Which leads me to two questions:

1. It seems that they believe it is ok to dive below 40m despite of nitrogen narcosis after training. What's the training that could make diver handle nitrogen narcosis?

2. Since NDL below 40m should be less than 10min, do they learn how to plan deco dive in their recreational diving course?

I can't speak for FFESSM, but I have been diving with the BSAC for some years.

Point 1. Maximum recommended depth on Air - 50m.
A large part of this is historical. BSAC divers with a Dive Leader qualification where historical qualified to dive to a maximum depth of 50m on air. At the time, the only breathing gas was air!.
It is now strongly recommended to use Trimix at depths beyond 40m. However, there are still parts of the world where BSAC members dive where access to Oxygen, and Helium is not available.
There is a very big awareness of nitrogen narcosis, CO2 retention, and degrading performance of equipment at depth. This is still covered in the syllabus.

Point 2. NDL limits
Integral to BSAC diver training is the concept of staged decompression diving. So BSAC divers (from Sports Diver on), are qualified to conduct dives involving compulsory staged decompression. The NDL limit is not a consideration, because it is not a limitation on our options. We may choose to stay within the NDL, or choose to conduct the dive with staged compulsory stops.


Both accelerated decompression and Mixed gas diving are not included within the core diver training program, although they are both discussed. They are additional course that can be appended to the core training and accessed as Skill Development Courses by specially qualified instructors.

Gareth

 

[nohappy]

Thank you @Gareth J ! That's very detailed. About point 1, as for nitrogen narcosis awareness, is it only taught on academic course or they do some progressive practices at depth underwater for training?

 

[Gareth J]

Nitrogen Narcosis is introduced in Sports Diver theory (Qualifications go Ocean Diver, Sports Diver, Dive Leader, Advanced Diver, First Class Diver). Sports Diver is also where redundancy is covered and rebreathers. When you qualify as a Sports Diver you initially have a depth limit, then with an instructor, you progressively increase the depth to 35m (maximum Sports Diver depth).
Nitrogen Narcosis is again covered, in Dive Leader, completing Dive Leader moves your depth limit to 50m (on air). There is a legitimate criticism that Dive Leader is more about leading inexperienced divers and managing incidents than deep diving. Having looked at the instructor notes, there is actually very little in the dive leader course.
Advanced Diver actually has some very good material on deeper diving, narcosis, redundancy, gases etc. However, the numbers progressing to Advanced Diver are quite low. Its got some quite challenging elements. The biggest stumbling point for a candidate has always been run a two day expedition to an unknown site/area. Getting instructors and divers together for this is not so easy.

 

[Gareth J]

I haven't really looked at this in any detail for some time. Having looked at the materials, and in view of your question, I have a few additional comments.

As a general rule, BSAC diving is club diving, i.e. you are a member of a club and mentored by other members. This is both a strength and weakness.
In my own club we have a number of members who are trimix qualified, some are CCR qualified. We do a wide variety of diving. In truth, the last 'deep' (Trimix) expedition was three seasons back. we did a lot of warmup dives prior to the trip.
We progress divers quite quickly to Sports diving. The majority of the branch diving is in the 25-45m zone. So progressing new members to Sports Diver is beneficial.
A very high proportion of members are on twinsets, I thing all those Sports Divers who have completed the depth progression are either using twinsets, or carry a pony for redundancy.
On most of our trips, dives over 30m, you are likely to see stage cylinders with a 'rich' mix, and divers accelerating their decompression stops.
As such, newer members are surrounded by divers who are very conscious of the risks of deeper diving, and conscious of diver redundancy. This is picked up by the lesser experienced.

This is a product of our branch (club). Other clubs may be far more conservative in their approach. One of our local branches dives mostly between 10-30m, but use small boats. There members are very good with charts, tide and small boats, not so good with deeper diving techniques.

We (my club) predominantly dive off hard boats. Twinsets and stages are less of an issue. If we dived from small boats (RIBs), then space would be more of a consideration, and twinsets and stages potentially less popular.

Gareth

 

[KenGordon]

There is a legitimate criticism that Dive Leader is more about leading inexperienced divers and managing incidents than deep diving. Having looked at the instructor notes, there is actually very little in the dive leader course.

On the other hand, a DL candidate will have typically done hundreds of dives (it might just be possible with 50) over several years. They will almost certainly have experience of narcosis.

 

[chrisch]

Both organisations allow decompression. FFESSM level 3 (CMAS 3 star) is a full decompression certification and higher than BSAC DL (CMAS 2 star). So to answer point two yes both do teach decompression procedures as part of their training systems. You are getting "tricked" (if that is the right word) by the widespread use of "recreational" to mean something it doesn't.

As to narcosis there is a great deal of debate about it but little real definitive understanding. A lot of people pretend that you can "get used to it" or "work up to it" which you cannot. You can persuade yourself that it is not affecting you if you experience it frequently but this is self delusion, not reality. You cannot "teach" narcosis or how to mitigate it.

Noticeable narcosis begins from about 3ATM PP N2 onwards. It's effects vary and certainly there are different outcomes for different people and different circumstances. It is generally agreed (although no scientific evidence to collaborate) that clear warm water is "better" than cold dark conditions. Whether there is less narcosis or it is just more tolerable in "nice" conditions is again up for debate.

Both of these organisations are what one might (rather unfairly) describe as dinosaurs. The 50m air limit comes from the military and was adopted when recreational (i.e. for pleasure) divers followed the military guidelines in the absence of other data. I can only assume the French navy had a 60m limit. FFESSM still uses the MN90 as a teaching tool - these are the French military tables.

In fairness there are many divers trained by both organisations that are more "modern" (again for want of a better word) in their thinking. BSAC introduced new trimix (Sports Mixed Gas) training a while back (and it is very good) but it has not yet adjusted it's air recommendations to suit. I doubt FFESSM will abandon the current system but if you dive in the Med area you will find a lot of younger divers use trimix and it is common for rebreather and other technologies to displace deep air. Some of the well know wrecks like Rubis (42m) are frequently dived on air, but the trend towards better gasses is unstoppable.

Both organisations encourage the move to better gasses to be fair. It is difficult to tell someone that has been deep air diving for many years they should stop. Hence the recommended limits persist. FFESSM is the slowest to adapt IMHO (I am level 3) but IANTD is becoming more popular in France and there is a very healthy "technical" diving movement. A surprising number of French divers are not interested in wreck diving or deep diving and are happy with "shallow" 20-30m reefs. My personal "limit" for air is 40m and I prefer some helium in the gas from 35m onwards. Rebreathers are slowly removing the need for any diving below 30m on air and will - I think - mean that very few people ever dive beyond 35-40m on air. If I had the time and money I would move to a rebreather myself.