Diving Schools

Introduction

There seems to be an ongoing battle between different diving schools and in particular between PADI and BSAC.
I don't know if this is the case in France with CMAS and PADI but since I started diving (with PADI ) people were taking the mickey
out of me (regardless of their nationality or their involvement with diving) for diving with PADI. Consequently I tried to find out what is the
difference, what is the "The Dark Side" of diving and unsurprisingly I was not alone in this quest. Loads of times divers ( PADI, BSAC or
crossovers) have asked "what's the difference?", "who is Better?", "why go PADI ?", "why go BSAC ?". Needless to say I have not found
the answer so far. Obviously like everything else there are advantages and disadvantages. Personally I know that if I had the time, the money
and the means necessary I would be doing all of them!!! and that's not just BSAC and PADI its all of them CMAS, SSI, TDI, ANDI ALL!!!

Scope

This web page is a try to answer the question of: "what is the difference between all these diving schools?". The truth is that for the time being
I will focus on the differences with PADI and BSAC but I hope that in the, near, future I will be able to include other schools as well.

Criteria

One way I see in comparing diving schools is by the diving tables that they are using. Since I am a BSAC diver I have BSAC '88
tables and I can use them! Also as a PADI diver I can use the PADI Recreational Dive Planner.
While searching the web for more information I came across other schools diving tables ( USN, CMAS, NOAA, etc).
I have not been trained to use them but their use doesn't look like rocket science to me. Having said that I must state that I wouldn't
dive with these tables and I wouldn't suggest to anyone to dive with tables that he (or she) hasn't been trained to use.
The following Criteria are going to be used for our assessment:

Criteria

1. Diving Tables - Single Dive
2. Diving Tables - Multiple Dives
3. Decompression Diving
4. Miscellaneous

Criterion 1 - Diving Tables, Single Dive

The following graph is a comparison of Maximum Bottom Time (MBT) allowed when diving using BSAC and PADI Tables. As you
can see both tables give the same MBT. For reference ONLY the BSAC MBT for Decompression Dives is shown.

Click here to see the dives used for this graph

First Dive Maximum Bottom Time

So in terms of MBT of First Dive it seems, to me, that there is no difference between either set of diving tables.

Criterion 2 - Diving Tables, Repetitive Dives

The second step is to investigate repetitive diving. Assuming the first dive to be the same (Max Depth and Bottom Time) and the same
Surface Interval (SI), then MBT for divers using PADI tables is three (03) times LONGER than for divers using BSAC tables, as shown
on the table below.

Second Dive Same Surface Interval

This time we will assume a buddy pair. One of the pair will be diving using PADI tables and the other using BSAC diving tables.
As we have already discussed the first dive will be the same. Now after any given time the diver using BSAC has to wait TEN (10) times
more than the diver using BSAC in order to do the second dive together.

Consider the following examples (Example 1 & 2)

The results of this exercise are shown on the following table:

Second Dive Same Maximum Bottom Time (MBT)

Results

The comparison between the BSAC and PADI diving tables shows the following:

1. For the First Dive both Diving Tables give the same MBT
2. For the Second Dive, assuming the same SI, BSAC diving tables give shorter MBT than PADI diving tables
3. For the Second Dive, assuming the same SI, PADI diving tables give longer MBT than BSAC diving tables
4. Planning Repetitive Dives with PADI diving tables requires shorter SI than using BSAC tables
5. Planning Repetitive Dives with BSAC diving tables requires shorter SI than using PADI tables

Discussion of Results

Danger for Decompression Illness (DCI) increases significantly with repetitive diving. This is why for Single Dives
both schools tables give the same MBT. The reduced MBT that BSAC suggests for the second dive compared to the longer one of PADI
provides extra safety in terms of DCI. The relationship between Surface Interval (SI) and MBT is not clear since for the same
SI the BSAC tables give 1/3 of the MBT that PADI tables allow while for the same MBT the BSAC tables require 10 times longer
SI when compared to PADI tables.

Conclusions

Diving using BSAC tables without Decompression stops gives less diving time than if diving using PADI tables. Diving using BSAC tables
requires longer Surface Intervals than if diving using PADI tables. The higher safety factor used for diving using BSAC tables reduces
the chances of DCI. PADI relaxes the safety factors to allow for longer Bottom Time (BT) and by doing so increases comparatively
the chances of DCI.

Diving using BSAC '88 tables for decompression dives extends the BT to longer times than PADI Recreational Dive Planner
(Non-Decompression Dives). Decompression dives increase the BT and also the chances of DCI.

All the above work is based on the assumption that there are divers that are planning their dives using Diving Tables and that
they actually execute their dives as planned. In reality tables are used mostly for training purposes while during the dive the diving
computer dictates MBT and decompression stops. Again there are advantages and disadvantages of this approach but it is not in
the scope of this page to examine that (I am planning another page dedicated to this argument).

It is useful to note at this point that Diving Tables are application specific and purpose made. Although the calculations are not shown
here I feel that I should say that it makes sense to have different diving tables for different application. The risk of DCI is related
to the dive performed that is Max Depth and Bottom Time. But it is also related to the physical condition of a diver. USN diving tables
were meant to be used by young, well trained and in very good physical condition divers where as BSAC diving tables are intended for use by
Recreational divers quite often older and not necessarily that fit. I would also expect to find that USN diving tables were compiled using male
divers mostly (I don't think there were many female divers in the US Navy at the time!) and it is known that different sexes have different response
to DCI.

Further Work

This work, so far, has dealt only with the comparison between BSAC and PADI Diving Tables. The following calculations and considerations
have to be included:

1. Input from Diving Computers for MBT and SI on the same sample dives investigated
2. The Comparison of other Diving Schools Diving Tables

Dimitris

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