I've recounted this before on SB, but this is the optimal place for it.
Back in the mid 90's, when George and Bill and I were still doing deep air dive, but would soon be switching to trimix.....for the deep air we were using the proceedure of Blow and Go at the end of a dive...the purpose to eliminate a huge additional decompression duration by all the time spent going from the bottom to 100 foot depth.... We had done 280 feet on the Rb Johnson/Coryn Chris, and at 25 minutes, were were all assembled together, all giving A OK that we were good to go. There were about 8 of us on this dive, one was a tech diver from England, visiting. He was using a new BC that had a bogus dump valve, but no one knew this yet.
On the signal to head up, we all fully inflated our bc's and began rocketing upward to the ceiling of 100 feet deep. The speed was intense. The OVP valve's on the BC's were screaming with ear shattering volume, and a wall of bubbles chased us from below....like being on top of lava on it's way to being ejected from a volcano
But faster
As you rocket upward, there is no difficulty keeping sufficient exhalation volume going, as the pressure differences are not so huge in each 30 feet you travel at this depth. We would have our eyes glued to depth guage/computers, to know about when to begin a massive venting of all air in our BC's. At about 140 we began venting, and the English guy near me was having trouble. I saw this, as did one other diver. I Vented all air, easily, and grabbed on to the English guy to make him heavier and help prevent him from blowing through the 100 foot ceiling. The other diver did this as well. Unfortunately, the English guy had one of those incredibly stupid 100 pound lift BC's, unlike the 40 pound lift models we used....the positive lift on his BC was so intense, that even as I pushed my feet on top of me and began swimming him down with over a 30 pound force, all 3 of us found ourselves on the surface about 6 seconds later.
It was a shock, but flashing in my head was the portion of the Navy Mixed Gas manual, that had discussed bubble formation, and hypersaturation. It specifically pointed out that in a scenario like this, there would be 2 or 3 minutes before the hypersaturation would have the bubbles forming, and I instantly realized it would be life threatening to remain on the surface for even a few seconds.....I told the english guy to use his knife on the bc and puncture it, and we would all meet at 100 feet. I and the other assisting diver then did a rapid weighted descent to 100 feet, where we stopped and saw the english guy reach us about 10 seconds after we reached the stop point.
George and Bill and the others all started making hand gestures to the English guy, mostly about if he was OK now, but also about the BC. No one was happy, but we decided to stay at 100 for 5 minutes instead of the one we normally spent there, and then did all our normal 50 foot time, 40 foot stop time, 30 foot stop....all normal for air profile. At 20 feet we switched to our O2 ponies ( 30 cu ft bottles). This was also normal for all these air dives, and the 3 of us used all the O2 in our bottles, as apposed to just 15 minutes as was more normal, if I remember correctly. We got out after everyone else, but each of us felt entirely normal, if not invigorated and energized, as always after one of these deep dives with O2 deco at the end. Whether the O2 deco, or lingering effects of the nitrous oxide from deep air the previous hour, we would always feel like kids on their Junior prom night when we were getting back on the boat.
So my thoughts on this thread...Had we not gone back down and recompressed, I think all would agree we would have suffered catastrophic DCS and likely died. Had we not all gone back down INSTANTLY, we would have suffered catasrtrohic DCS. Had we not had the O2 bottles with us, the outcome may have been very different, meaning much worse---However, if there had been all the bubbling suggested in much of this thread durring the rapid ascent, we would NOT have made it to the 20 foot stop with all the long air stops we did at 50 feet, 40, and 30 feet. The bubbles would have been so out of control by then, that we should have been incapacitated before reaching the 20 foot stop. In fact, we felt entirely normal, although significantly nervous and tentative, as we were going on a theoretical , that none of us had ever heard of being tested.
As a useful piece of theoretical discussion here, I think this applies to air and Nitrox divers in their depth ranges, and has no bearing whatsoever on Trimix divers, as Helium would NOT stay in solution in the blood on such an ascent, as air is capable of doing ( hypersaturation would have occurred well before hitting the surface had we been on trimix).
I realize this flies in the face of much accepted agency teaching. This was a factual occurrence, with many witnesses, and it is very relevant to the understanding of the phenomena being discussed in this thread. I think it would be negligent of me to withold the re-telling of this account, just because it may not mesh well with Agency positions at this moment in time.
