Mailing List Archive Mailing List Archive
> Fine, how much deeper can you go on air without exceding them anyway? Are >1mn deep stops that much safer than a slow ascent for such profiles? Do you >have anything else than opinions about that, or any kind of experience? >Apparently you don't do any deep air diving, so how do you know what you're >talking about? Do you? I do have a significant amount of "deep air" experience, under controlled conditions. When I was an instructor at the Naval School of Diving and Salvage, we would regularly run 200' qual & re-qual dives on air in our pressure complexes. We also ran 285' "Narc" runs with HeO2 students. With divers in surface supplied equipment, in 8' of actual water pressed down to the bottom pressure, solid communications, and under the watchful eye of a Navy Master Diver who could look through a porthole at the divers. Now I think I can make some fairly authoritative statements about the environment. At 200' on air most divers are significantly impacted by narcosis. With concentration, they are usually able to perform assigned tasks reasonably well. In surface supplied gear where a topside support team can monitor their progress (and restrict their depth or pull them up if needed) this is a reasonably sane kind of operation. In SCUBA where the diver must be able to evaluate all diving requirements and act independently this risk is clearly unacceptable. At 285' virtually all divers are dramatically affected by narcosis. A significant number can complete assignments, but only with great effort and concentration. DCS cases were experienced approximately once per month, virtually all type I and treated immediately upon recognition in our on site chambers (not a luxury most civilian divers have). Needless to say, decompression was accomplished with conservative use of the Navy Dive Tables. Interestingly enough, more DCS cases seemed to arise from 285' chamber runs than from in water. For what it is worth, I am not aware of any O2 toxicity cases. Keep in mind that the population involved were Navy divers whose physical condition may not be typical of the diving population. Also at that time all Navy divers were pre-screened by having to breathe 100% O2 in a chamber at 60 fsw for 30 minutes without O2 toxicity symptoms. That requirement has been since dropped since the medical types believe it is meaningless. Bottom line --- deep air on SCUBA is just an unacceptably risky proposition. Anyone who says otherwise is ipso facto a dangerous idiot. Almost anyone can SCUBA dive recreationally. More demanding diving requires more education, preparation, and especially discipline than many people are willing to expend. It is not, repeat not for everyone. Until this message is widely understood, expect the carnage to continue. Now is that polite and professional enough or do I have to call someone bad names? Be advised that WAS also covered as a part of Navy diving ciriculum. B.L. Flank -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
Navigate by Author:
[Previous]
[Next]
[Author Search Index]
Navigate by Subject:
[Previous]
[Next]
[Subject Search Index]
[Send Reply] [Send Message with New Topic]
[Search Selection] [Mailing List Home] [Home]