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Brad May writes: > Am I missing something? In adjusting your tables, you're assuming that > you have been at 8000' long enough to have outgassed N2 accumulated at > whatever (lower) altitude you came from and are at equilibrium at 8000'. > All the tables (and computers) I'm aware of assume that you start at N2 > equilibrium. Not true, actually. Methods for adjusting tables include a procedure for dealing with dives that must be made before a diver can be equilibrated to altitude. In the case of the USN tables, this is simply a chart specifying what repetitive group letter designation the diver should consider themself upon arrival at altitude. Many computers also have a procedure for making this adjustment. For example, the ORCA Delphi can be activated at departure altitude prior to travel to the destination altitude. Upon arrival, it will correctly account for the excess nitrogen still in the subject's tissues (I've actually tried this, just out of toy-curiosity after I first got my Delphi and went from the San Francisco Bay Area to Lake Tahoe, elev. 6200' -- it was pretty cool to see a loading in several of the theoretical compartments just from going to altitude). In the case of most computers, however, these procedures are usually not available in the case in question, as the actual dive will be taking place at sea level, not at the anticipated cabin pressurization of the aircraft. Dave Waller YMCA Instructor dwaller@cu*.hp*.co* Hewlett-Packard Co. (408) 447-4413
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