Safety Stops and old practices

[sourcearun]

Well, in India CESA and Safety Stops are very much part of current PADI training. Becomes a second nature over a period of time, and its safer that way too!

 

[Reg Braithwaite]

Obviously we did not die or suffer any negative consequence.

Ever hear of a little thing called survivor bias? The dead divers aren't here on the board to debate with you. Neither are the ones that quit the sport because they found diving depressing and never realized they were suffering from sub-clinical DCS

 

[Diver0001]

Yes we knew what we were doing.

He who does not know the depth of his ignorance may make the most serious mistakes of judgement with complete confidence and conviction.

I know I have.

The real test of knowledge is, would you advise people to dive like that *today*? I think the answer across the board, from anyone who has been keeping up to date on developments since the early 80's would be a resounding "no".

I know you like to brag about the old days, N.., and I wouldn't want to take that away from you. But be careful of setting a poor example because things really HAVE changed.

R..

 

[Reg Braithwaite]

Anyone's 'first-hand testimony' amounts to "n = 1". It is valid (to date) for that one person only. It may or may not be valid for others.

+1!

An ex-colleague has a memorable way to express this idea: The plural of "Anecdote" is not "Data." Even when you have an overwhelming collection of first-hand testimony, you do not have data. Data needs to be rigidly controlled for bias.

For example, every single person replying to this thread might say that diving a contemporary dive computer is safer than following the Navy tables. These are still anecdotes!

We don't know whether they have tried both under controlled conditions and had better results with the computer. We don't know whether there is some cultural bias such that the kinds of people who buy fancy computers are the kinds of people who like to post in Internet forums. We don't know whether there is a placebo effect: maybe when trying the Navy profiles we have to reprogram a computer so that our test subject think they're diving a computer.

Good test data is hard to come by. Everything else is "anecdotal evidence." Useful, to be sure, but it isn't the same thing as data.

 

[Gary D.]

not to say that they want to use them up, but it's a mission. it may be important enough to lose lives in making sure it gets done.

not so with recreational divers.

I don't know where this attitude comes from, maybe Hollywood but it is not true at all. DO NOT include SEAL's or other service combat divers in this as diving is NOT their primary job. So back on track, it doesn't matter what the job is they are not going into something knowing a diver is going to die just to get the job done. There is always another way.

Military Divers are trained very different than any other type of diving. From the outside looking in a lot of non-military divers think they are nothing but a bunch of reckless fools. A military diver has the right, no questions asked to refuse to do a dive. Yes even the military realizes that not everyone is up to speed all the time and ready to dive all the time.

The military has restrictions of not exceeding your training level and they are very strict about it which ISN'T the case in the recreational diving world.

Gary D.

 

[Diver0001]

"Hey Lenny"

"Yeah boss"

"I want to to take this gun and go sneek up on the enemy under water and shoot as many of them as you can before they kill you"

"uuuhhh sure boss... anything else?"

"Yes, if you diver deeper than 33ft I'll kick your butt!"

 

[Brian Sharpe]

+1!

The plural of "Anecdote" is not "Data."

I could not have said it better!

 

[Blackwood]

People need to realize that the Navy Tables are just that. They were developed around Navy Divers who are young and in the best condition anyone can be in.

What's I find important to note is that (to my understanding) Navy missions generally didn't call for repet dives, so the pragmatism of using a Navy model to plan repet dives can be questioned.

Exactly!

And as for me, I myself would rather give up 5 minutes.

Better safe than sorry.

Given ascent rates in the 30s, safety stops are superfluous with respect to the prevailing decompression models.

So, respecting the adage 'better safe than sorry', why 5 minutes? Why not 10? Or 15? Why on backgas instead of Oxygen?

In other words, how are you drawing the line between 'safe' and 'superfluous' in trying to avoid 'sorry'?

 

[nereas]

...Given ascent rates in the 30s, safety stops are superfluous with respect to the prevailing decompression models.

So, respecting the adage 'better safe than sorry', why 5 minutes? Why not 10? Or 15? Why on backgas instead of Oxygen?

In other words, how are you drawing the line between 'safe' and 'superfluous' in trying to avoid 'sorry'?

Excellent question!

Here is the thought process, with an example.

Premise (anecdotal): all dives are deco dives.

Corollary: all NDL dives performed without safety stops are an unnecessary risk.

Issue: how long should the safety stop be?

Rule: 1st stop = 1/2 MOD for 1 min, then 1 min stops thereafter for every 10 ft of ascent.

Example:

MOD to 100 fsw within the so-called NDL limits.

1st stop = 1/2 MOD at 50 fsw for 1 min.

2nd stop = 40 fsw for 1 min.

3rd stop = 30 fsw for 1 min.

4th stop = 20 fsw for 1 min.

Final stop = 10 fsw for 1 min.

Total safety stop time = 5 mins.

Try it for 130 fsw or 30 fsw or anything in between, and it adjusts the stop time nicely, for all so-called NDL dives.

 

[nereas]

Hmmm, who to listen to -- ...

Listen to yourself Peter. That is the only person who is responsible for you.

If you fret away your entire life worrying about whom to listen to, you will have missed the entire point of your inner voice.