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The answer you received is debatable. Rounding your example to a 3,000’ ascent, the standard atmospheric pressure at 3,000 feet is 13.17 psi. So the pressure change from sea level to 3,000' is 1.53 psi (14.7 - 13.17). If this is compared to a 3,000' ascent from 6,000' (11.77 psi) to...

A valid point, but tech divers routinely perform safe deco on O2 at 20' and if anyone is using pure O2 they are hopefully adequately trained prior to using it. Also if a diver is simply performing a safety stop on a no-stop dive the exposure is very small.

Yes. Staying under pressure minimizes any "bubbling" and increases the driving force for gas elimination. Keeping this simple (and not exact), by definition the pressure inside a bubble is equal to the external pressure (since that is what determines when a bubble stops growing) and due to the...

The reason is the reduction in atmospheric pressure. Are you decompressing properly to surface after a dive (to 14.7 psi) or decompressing for a reduced pressure? If the ocean decompression is conservative, then flying right after may be a possibility. If you are decompressing just to reach...

Yes, anytime the pressure is reduced the partial pressure of the gasses are reduced. But the issue is the partial pressure of the inspired inert gas. It is the difference between the tissue tension and that of the inspired inert gas that determines the rate of off-gassing. When on O2, it is...

I’ll apologize for the length of this post in advance. The simple answer is the statement of bringing the diver as close to the surface as possible to eliminate the dissolved phase assumes the diver is on a gas containing inert gasses. Once on oxygen, coming closer to the surface does not...

I just have to diasagree with your instructor. I think helium as gotten a bad rap in the past from not being understood and many tails have developed from it. First I doubt anyone going to that depth is so unskilled that an uncontrolled ascent would occur. Second, the fact that narcosis will...

Sometimes it is easy to misread emails and posts ... sorry. I wasn't trying to limit my answer to my software and was trying to answer it in general. Regarding your question about Departure specifically, other than some rounding that may occur, there would be no difference in deco time between...

Staying at 20' should not increase the decompression once on O2. The gas elimination rate is based on the gradient between the tissue tension of the gas and the partial pressure of the gas being breathed. So once on O2, no inert gas is being breathed and the gradient is at it's maximum...

A bubble is a bubble. As others have said, the content does not matter. Bubbles are also not separated into different kinds such as air, nitrogen, oxygen, or helium. A bubble may contain any of the gasses depending on your breathing mixture, but the off-gassing will not result in different...

Several things have been brought up. I agree with doing more deco at 20 feet due to keeping microbubbles smaller, which keeps a higher surface/skin tension squeezing in on microbubbles. Of course a very slow ascent from 20' to the surface as Doppler also stated is advisable and I also agree...

Thanks. I will try to get some more info.

Hi Schoc369. Not to get involved in some good debates ... the answer depends on the question. Azza's approach is the easiest and simplest. Beginning half-time compartment lessons will just be interested in the "uptake" or "elimination" as it is an easy reference point and visualization of the...

I'll double check, but no belching due to swallowing air as I recall since I asked that question ... and again, only starting during the ascent (could be coincidence since it took a certain amount of time to "get ill") and then she continues to stay sick.

I had a friend approach me with a situation I have never heard of or encountered before, so I thought I would throw it out on this forum. The situation is a recreational diver starts vomiting during the ascent portion of her dive. It does not happen on the bottom phase, but only during the...

Diver0001 is right on. To off-gas there must be a gradient, i.e. the difference between the tissue gas tension and the partial pressure of the inert gas being inspired. The greater this difference the faster and more efficient the off-gassing will be. This occurs by two mechanisms. One is by...

Yes, some people have done something like this. I certainly would not want to.

I agree with Dr. Deco ... good thing since he's the doc. Putting aside the medical considerations of being in the water that long in a wet environment, among other issues, a 24 hour dive to 4 meters is very benign and even the utmost conservative profile would not require any decompression or...

You may want to ask this in the Diving Medicine forum.

As just said, computers do not bend. You have a grasp on the simple deco theory, the problem is that it is much more complex to the point of the experts not having it figured out yet. Slow compartments can become the limiting ones, but the other compartments may not be resonding as the...