I was on a dive where the depth was 90ft ... I used 2474 psi during the dive and started with about 3100-3200 so when I surfaced I had between 626-726 psi so I would have had time to take a slower ascent. In addition, my computer said the dive lasted for 17 minutes.
...So when I got to 1100 psi I told him we needed to head up.
We started to ascend and at first I was having trouble going up because I had emptied all my air
As TSandM pointed out, it is very unusual for divers to pull another diver to the surface a was described. I am trying to understand things from their point of view to see if I understand why.
The diver said that when she signaled to the others that she wanted to ascent, she had 1,100 PSI, meaning she had used 2,000-2,100 PSI at that point. We have established that her SAC rate for the entire dive was about 50 PSI or 1.25 cubic feet for that dive. She was at 90 feet, or 3.73 ATA. That means she must have been breathing her air at about 3.73 * 50 = 186.5 PSI/min. She said she surfaced with 626-726 PSI, meaning she used about 400 PSI on the way to the surface, without doing a safety stop. If we assume the average depth of her ascent was 45 feet, then the direct ascent to the surface from 90 feet took nearly 4 minutes, or about 22 feet per minute.
So let's say I am her buddy at the point at which she says she has 1,100 PSI and wants to ascend. I am startled. Given a typical descent rate, we are only about 12-13 minutes into the dive, and she is ready to ascend? Assuming I have a SAC rate typical of a diver with that experience and that I started with the same amount of air she did, when I look at my gauge I see that I have more than 2,200 PSI--maybe as much as 2,400 PSI. What goes through my mind at that point? I'm thinking that I have a dive buddy who is really going through gas in a hurry. Am I able to do the math and calculate how fast and decide if she is going to go OOA before the end of the dive? Not under those circumstances. In the comfort of our homes, though, we can do those calculations. We can see that at the rate she was breathing air at that point in the dive, and with the amount of air she reported that she had left after her direct ascent to the surface without a safety stop, she would have been OOA by the end of that dive if she had stayed at that depth for about 3.5 more minutes. (Divide the 626-726 PSI she said he had at the end by the by 186.5 PSI/minute she was breathing at that depth.)
So I'm concerned at that point, and I want to get her going up. She then dumps all of the air from her BCD and has trouble ascending. She is trying to go up, but she is getting nowhere. Now I'm really getting worried. I try to hurry her along. Once she is going up, I still think she is going too slow. (She said that her computer indicated that at some point in the ascent she had exceeded the safe ascent speed, yet the entire ascent was a slow 22 FPM. That means the rest of that ascent was very slow indeed.)
I guess this helps me understand a little better. They probably could have handled things better, but I think I can see why they showed so much concern.
