15' Safety Stop vs Minimum Deco

[Uncle Pug]

~Thanks to Aaron for the question~

Question:
Which is better: a 15' safety stop or Minimum Deco of 1 minute at 30', 20', 10' for recreation NDL dives?

Please give your reasoning and/or supporting evidence.
Remember the forum is Basic Scuba Discussions.

 

[sillygrendel]

I would like to.

Anyone care to post links to info on deco theory? I'd much rather read that than hear personal opinions...

From what I gather, deeper stops are a good thing.

 

[ChrisM]

I've got a bunch linked at Underwater Planet - Links under Decompression Theory. Got sick of looking all over the net for them.

Chris

 

[AquaTec]

Uncle Pug once bubbled...
~Thanks to Aaron for the question~

Question:
Which is better: a 15' safety stop or Minimum Deco of 1 minute at 30', 20', 10' for recreation NDL dives?

Please give your reasoning and/or supporting evidence.
Remember the forum is Basic Scuba Discussions.

In Basic Scuba I would first refrain from even using the word Deco.
Second is their an agency out there promoting these stops to Basic scuba divers [i think i kow the answer, but just verifing]
Third in basic scuba I will assume we are using air as a breathing gas
fouth would we establish that a Basic scuba diver has less than 50 or at most 100 dives
fifth as Basic scuba the divers are doing dive no deeper than 60 feet so the 30 foot stop would be at half the overall depth.
well lets say we extend this to 100 feet as this is probably what most are doing anyways.

I think that Phisyologicaly the 30/20/10 method is probably better.
the 30 and 20 offering a higher po2 the 10 being a waste of time.
Reality a basic scuba diver would be vert hard pressed to hold a 10 foot stop. at 30 feet on air they are still ongassing [pn2 1.58]
even with the higher po2 I would say that their most benificial stop is the 20 foot stop. as their pn2 is lower and yet the po2 still offers some pressure gradiant. I also think that most Bsaic divers would be hard pressed to remember, bother to, or have gas management skill sto feel they needed to accomplish three stops before surfacing.
so with all the above that I have rattled on about, one stop is probably best in real life with the wide spectrum of basic divers out there, some only diving once a year or less. and the added benifit being marginal at best for three stops at a mninute each over one stop for three minutes.

I would pick one stop at 15 for three minutes or better yet five. howcome 15 feet was picked is probably because it is 1.5 ata [roughly] more than likely it is just a number that PADI picked and then promoted. probably based on the slightly less time it takes to get to the surface when you run out of air trying to perform your safety stop.

15 feet for 5 minutes

 

[WreckWriter]

I think either one is pretty safe so.....

I'll take a different direction in my answer. I'm not going to look at physiology but rather at logistics.

For the average rec diver the single safety stop is better in that Joe Average Diver doesn't have the buoyancy, discipline, or concentration level to properly manage a series of three stops. These things only come with years and dives.

Tom

 

[ckharlan66]

I have to agree with Wreckwriter. Doing it in stages is probably better, but, probably not necessary or practical for all recreationaly diving.

Chad

 

[neil]

Let's see:
The original research by Pilmanis showed that a stop in the 10 to 30 ft range for 3-5 min. was beneficial to reducing silent bubbling. If you do the 30, 20, 10 stops, you will not only be pausing in that range for a bit more time, but guaranteeing a slow ascent to 10 ft. For that reason alone, I think it's a better idea than just a stop at 15'. Which ought to be enough for Basic Scuba Discussions.

The only sure way to know would be to do actual tests with divers and Doppler ultrasound, no? Probably been done. How do I know? Because Pug never poses a question he ain't got the answer to.

Neil

"Few things are harder to put up with than the annoyance of a good example."
-Pudd'nhead Wilson

 

[raxafarian]

Uncle Pug once bubbled...
~Thanks to Aaron for the question~



Remember the forum is Basic Scuba Discussions.

My opinion:
Make your first stop at 40ft for any dive 80 ft or greater. 1 minute at 40, 1 minute at 30, 3-5 minutes at 15/20ft.

For dives 60-79 ft, 1st stop at 30 for 1 minute, then 3-5 at 20ft.

Dives less than 60ft = 3-5 at 20ft.



If you just want to do the 'standard' 3-minute stop, at least extend it to 5minutes, and make sure your ascents are nice and slow, especially once you reach approx. 1/2 your max depth.


I based the above on.... a guess.

 

[ckharlan66]

Pug never poses a question that he don't already know the answer too (or at least has a strong opinion.) But hey, it gives us all a chance to rattle his cage a little. Ain't it fun.

Chad

 

[redacted]

If, by better, you mean a statistical difference in the incidents of DCS, I would think it will be a toss-up. Either of those techniques should get the same results in terms of avoiding a trip to the chamber. Beyond that, the simplicity of 3-5 minutes at 15 ft (10 to 20 ft in practice) probably is more important than any difference in off-gassing for recreational divers. Although my DSMB is knotted at 10, 20, & 30 ft; so my options are open.