20' Safety Stop

[av8er23]

I have a question and think I already know the answer. Is making a 20' safety stop in 20 feet of water the same as doing it in an air box at 20'? The pressure in the box and the water are equal right?

 

[NSDiver]

Yeah.... but why do you ask?

 

[Gary D.]

Sure but make sure the air in the box is good first.

Gary D.

 

[alpaj]

Hey, pick me pick me. Ahh what is an "air box"? Sorry had to ask sounds too funny

 

[Rick Inman]

Is making a 20' safety stop in 20 feet of water the same as doing it in an air box at 20'?

I spent some time in a tube full of air at 20' (and other depths). It was just like water, except I was dry and watching DVDs.

(the above post seems, at first, flippant, but in fact, really does answer the question)

 

[Warren_L]

Hey, pick me pick me. Ahh what is an "air box"? Sorry had to ask sounds too funny

A box or pocket of air at a depth of 20'. Providing it's breathable, breathing the air in this pocket is the same as doing a safety stop on scuba (assuming air on both).

 

[BigJetDriver]

I have a question and think I already know the answer. Is making a 20' safety stop in 20 feet of water the same as doing it in an air box at 20'? The pressure in the box and the water are equal right?

This is a somewhat misleading question. Think of it this way, however, and it may be a bit more understandable.

If you mean, by the term "air box", a box or column that has its floor at 20 fsw, but the top is open to the surface, you have a caisson.

The pressure is equal to the pressure developed by the column of air down to the surface PLUS 20 more feet of air molecules. This pressure is NOT the same as the pressure on the diver in the water at the bottom of the column, because the pressure on him is the pressure developed by the air column to the SURFACE, plus the weight of the water column down to 20 fsw. The water weighs a lot more per cubic inch than the cubic inches of air inside the caisson. Ergo, the pressure in these two examples is different at the same 20 feet of depth.

 

[Whatgoesdown]

Depends upon whether the box is open at the bottom or at the top.

 

[scubapolly]

I have a question and think I already know the answer. Is making a 20' safety stop in 20 feet of water the same as doing it in an air box at 20'? The pressure in the box and the water are equal right?

I assume you are refering to something similar to a diving bell? Perhaps like the box they have at Blue Grotto in Florida? The air in a pocket such as this will be compressed to whatever depth the base of the air pocket is at. If the "box" you are refering to is like the one at Blue Grotto it has fresh air pumped into it, and there fore it is safe to breath for as long as you need, you can hang out there with no reg in your mouth for your entire stop, if there isn't surface supplied air you can use the air pocket to hang out but keep your reg in your mouth to breath.

Hope this answers your question.

 

[BigJetDriver]

Depends upon whether the box is open at the bottom or at the top.

Well, see my definition above. If you are not defining it that way, then see the pictures in the PADI OW book.