DECO vs DEEP stops

[neilg]

Can a seasoned veteran diver please help me understand what the difference is between a DECOMPRESSION stop and a DEEP stop? Why are they "presented" as different conditions/events in my dive computer documentation or is it all just a matter of terminology ...to confuse the "not so seasoned" rookie diver?

Thanks !

 

[chrpai]

In the purist sense, all diving is decompression diving. That is you observe protocols such as safe ascent rates and safety stops and you are in fact coming out of compression.

A deep stop is just a safety stop at a deeper depth. A safety stop / deep stop is just a form of voluntary decompression stop.

In the strictest sense, a DECO stop is a mandatory stop.

Clear as mud?

 

[windapp]

Not a veteran, but I do know the answer to the question.

While deep stops, and safety give you an margin of safety against the current data not necessarily fitting your particular circumstances, that is not their primary purpose.

The main purpose of non-decompression stops is to give your body a chance to off-gas microscopic bubbles that have already formed in your tissues and bloodstream. This is different from a decompression stop that is used to bring the level of disolved nitrogen in your tissues down to an acceptable level before ascending further.

As a recreational diver, you are not supposed to have to do decompression steps. If you have a decompression obligation, you now have a ceiling above you beyond which you cannot safely pass without an unacceptable risk of DCS. Sure, you can do the stop to clear your obligation, but, if you don't have the appropriate training and equipment to dive in this "overhead" environment, your risk of injury has substantially increased.

Deep stops and safety stops, on the other hand, are there to ward of the potential long term health effects of allowing microscopic bubbles to stay in your blood stream and tissues. You can skip them without doing yourself any immediate harm, but long term, you are best to do the stops.

 

[Superlyte27]

I'm sure this will be explained 300 times in the next few days. And as they say, if you ask 10 different people you'll get 11 different explanations. So, I'm going to reserve my explanation. But, I will ask you this question.

Imagine you have a balloon and a box with a hole in it. At the surface, a fully inflated balloon will not fit into the hole in the box. The hole is too small and the balloon is too big. But, at 100' the balloon that was fully inflated is significantly smaller. It'll easily fit into the hole. It will at 66' too. But at 33', the balloon is just barely too big to be fit into the box. See an issue here?

So, you've made a dive to 200' and played around for a little while building up some nitrogen in your system. You've come up to do your deco and at 20' you do a mandatory stop of, lets just make numbers up and say, 10 minutes. But, at 20' that bubble of nitrogen won't fit through the cells/tissues in your body. The nitrogen is the balloon, and your cells/tissues are the box with the hole in it.

Do you see the problem that can arise with doing all of your deco at one stop?


*EDIT*
A deep stop IS a decompression stop, just at a deeper depth than say 10', 15' or 20'. Whether you do a deco stop, deep stop, safety stop, you are decompressing as you absorbed nitrogen under pressure.

 

[chrpai]

Of course typical recreational dive training skips all this theory....

 

[Superlyte27]

Of course typical recreational dive training skips all this theory....

In recreational diving, if everything goes as planned, the balloon should NEVER be bigger than that hole in the box, even on the surface.

 

[chrpai]

In recreational diving, if everything goes as planned, the balloon should NEVER be bigger than that hole in the box, even on the surface.

Agreed, with the caveat that *should* is a probability not a guarantee. (Assuming we are speaking the same metaphor. )

 

[windapp]

I'm sure this will be explained 300 times in the next few days. And as they say, if you ask 10 different people you'll get 11 different explanations. So, I'm going to reserve my explanation. But, I will ask you this question.

Imagine you have a balloon and a box with a hole in it. At the surface, a fully inflated balloon will not fit into the hole in the box. The hole is too small and the balloon is too big. But, at 100' the balloon that was fully inflated is significantly smaller. It'll easily fit into the hole. It will at 66' too. But at 33', the balloon is just barely too big to be fit into the box. See an issue here?

So, you've made a dive to 200' and played around for a little while building up some nitrogen in your system. You've come up to do your deco and at 20' you do a mandatory stop of, lets just make numbers up and say, 10 minutes. But, at 20' that bubble of nitrogen won't fit through the cells/tissues in your body. The nitrogen is the balloon, and your cells/tissues are the box with the hole in it.

Do you see the problem that can arise with doing all of your deco at one stop?

I don't see how this deals with the original question. The OP asked about a no-deco deep stop vs a decompression stop.

 

[Superlyte27]

No he didn't actually. He asked what the difference was between a deep stop and a decompression stop. Then Chrpai answered his question and said they were the same thing. Then I enlightened readers on why deep stops are necessary through an analogy.

 

[neilg]

Thank you all for the education and in particular the "box and balloon" scenario which was a simple but highly effective illustration of some of the hazards deep diving has to offer. I totally agree, as a rec diver I hope never to deal with such a situation and just wanted a better understanding of the physics involved. And even 11 answers could be helpful because each might add a different perspective, experience and understanding of a rather complex issue, which is what makes this online community so great. Thanks again!