Safety stop body position

[knotical]

That is not off gassing. Gassing, on or off, is the movement of nitrogen at the tissue level.

Here is a good article that touches on the subject, NWGratefulDiver.com

I guess off gassing is the wrong term...

I'm not convinced that off-gassing is the wrong term. In general, off-gassing refers to gases returning to a gaseous state, such as coming out of solution. Isn't that what happens in the alveoli? In scuba, I always thought off-gassing referred to the entire process, from tissue to blood to exhalation.

In scuba, nitrogen also returns to the gaseous state as silent bubbles, and/or as symptomatic bubbles. That's not off-gassing, that's the bends.

 

[PfcAJ]

There are two things going on here, and y'all are trying to use one term for both of them.

#1 Off-gassing at the tissue level - gases moving across membranes into the blood (also a "tissue")
#2 Off-gassing in the lungs - gases moving across alveolar membrane into the inspired gas, on its way to be exhaled shortly

Both are "off-gassing", and while they are separate ideas, its tough to have one without the other.

Gas in bubble form can be effectively eliminated by the lungs. This is normal and a-ok (to a point). Gas in dissolved form can be effectively eliminated by the lungs (this is always a-ok). Imo, the pressure differential from being vertical vs horizontal is probably low enough to be a non-issue for most divers. Probably. I've yet to see any evidence to support a position one way or another, but I hypothesize that horizontal is better for deco, even if the advantage is slim.

A more pragmatic reason for being horizontal is so you can swim easily (help buddy, say near the ascent line, stuff like that) and to present as much resistance as possible to vertical movement (ascending or descending). Clearly, doing the last 5-10ft vertical and with your head on a swivel is prudent if there are boats around or other divers possibly above you. Other than that, I vote for horizontal all the way up.

 

[randytay]

Horizontal. Compelling reason? Because I can.

 

[DaleC]

If I'm coming up on a line, any position is fine. If I'm doing a blue-water ascent I prefer being vertical. Here it's easier to be slightly negative and gently fin up. It's just easier to control the rate of ascent this way.

My experience too.

If I am ascending along some sort of fixed reference point (shore, up line etc) I tend to be horizontal because that's generally how I'm oriented and I'm used to dumping the wing from the rear hip and rolling to dump from my left shoulder (DS).

If however, I am ascending in the water column (low vis) with no reference point, I do so vertically. In this case I am riding my depth gauge and trying to remain just a touch negative so I can make small adjustments to my position with slow kicks.


The main point with a safety stop is that you are not decompressing (you should not have accumulated enough N to make that necessary) but rather, slowing your ascent rate. Therefore, in reality, any position that allows you to control that ascent rate is ok (boat traffic not withstanding).

 

[PfcAJ]

If you're not decompressing, what do you think you're doing during the ascent and safety stop?

 

[The Chairman]

If in a vertical position does t really make a difference where your feet are? Your lungs are where the off gassing occurs. So with your lungs being under less pressure than you lower extremities wouldn't you still off gas the same?

Your lungs and your entire respiratory system are exposed to the ambient pressure of your regulator. The air pressure inside your lungs does not vary except by the negligible weight of the air. It doesn't matter if you are right side up or down, horizontal or vertical. However, the position can affect work of breathing negatively, so be in tune with that.

Otherwise, the environment and your comfort should dictate your position. If your thang is always being horizontal just because you can: go for it. If, like me, you feel more relaxed on your back with your feet slightly down like you are on a chaise: that's fine as well. Just be sensitive to the environment around you.

 

[herbdb]

I like to easily see where I'm going. On blue water dives, I usually descend horizontal and ascent vertical. Going up this makes it easier for me to see divers and boats above me.

 

[nimoh]

I prefer horizontal mostly because most of my diving involves looking at things on the bottom, and being horizontal gets my eyes about 5' closer to what I am looking at. I also dive in a lot of silty environments, so being horizontal keeps my kicks away from the silt. It also puts me in a better position to move quickly to help out a buddy, or to move quickly to a buddy to get help.

On a drift dive along a wall, it doesn't matter as much since you can get your eyes close to the wall equally as well in a horizontal or vertical position, however, if you get too close, it is much easier to back up in a horizontal position than in a vertical position (providing you can do a back kick).

On an ascent, I think the difference matters even less, but I use this time to practice my horizontal trim to make the rest of my diving more enjoyable and of course the buddy aid thing still applies. If doing a safety stop in a current, I think a horizontal trim would make you more streamlined and better able to maintain position.

Basically, I can think of a lot of good reasons to be in a horizontal position, but the only one I can think of for vertical is that it tends to be a more natural and comfortable position. So, I am working on trying to get a horizontal position to be more natural and comfortable for me. Currently, I have to focus on staying horizontal and in trim, and consciously correct myself if my head or feet start to drop, but hoping to get to the point where it is all automatic.

Even though I prefer the horizontal position, I would never call someone names for diving vertical. I may point out a silt cloud caused by a stray kick, but I would do the same to someone in a horizontal position. If you dive vertical, don't stir up the bottom, and don't kick the reefs, then I would be happy to dive with you.

 

[fjpatrum]

I do mine horizontally, usually, because I'm trying to practice being horizontal and still. I think, though, it all depends upon what is appropriate for the environment. In a boat heavy area, for example, I'd be far more likely to be vertical. I don't think it really matters that much in the end.

 

[fnfalman]

I do my safety stop with my body horizontal BUT face up so that I can see what's going on at the surface.