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Posted : August 31, 2009
hi please can you help, i have been taught to have a safety stop at 5 metres for 3 minutes however my partner says that this should be 6 minutes at 6 metres, who is correct or which is safest ?

Posted : September 1, 2009
An interesting question... decompression theory is at its simplest level just a set of mathematical algorithms that through a lot of dives have been proved statistically to work - they are not a perfect 100% accurate and true state of your specific physiology at that precise point in the dive...

An odd way to start answering perhaps...

some of the tables (and hence read differing training agencies) have developed 'rules' on safety stops which is why your partner is suggesting something slightly different.

Without a doubt - verify you were taught correctly by checking your manuals and reference materials (eg tables) and do what your training said... some tables are very very different as to how they define dive bottom time.

Clearly you will have been taught about no decompression limits and if you slightly overstay your bottom time (see your tables for rules) - never mix rules of decompression diving with non-decompression diving... nor transfer pressure groups and other residual nitrogen times between tables - very very bad thing to do.

Now from a technical perspective... the stop done at 5m can be done at 5m or 6m safely... the longer time at that depth such as 6 minutes is also safer so long as air or gas supplies are abundant and that you are warm enough etc IT IS KEY though that your ascent to the surface from this stop (as it is in the last 10m of water were the largest pressure changes occur), is slow and controlled - this by far has SIGNIFICANT benefits to you followed by relaxed exit and careful exit from the water (ie non-strenuous) and then a good 5 to 10 minutes relaxation on the boat or shore during which you hydrate with water.

Hope this helps, Andrew.
Answer provided by ADM Diving

Andrew Dawson-Maddocks
The views expressed by the author are their own and the publishers accept no liability for the advice and views expressed by the author, or other users, which are provided as a general service to divers. Users are warned that secondary posts are the views of other users and may not be technically correct.
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