Regarding dci you dive for recreation you work in a zinc mine that is anywhere from 1600 feet below the surface to 3000 feet below does anyone out there have any information on this and decompression?

Answer 1

I doubt PADI (or any other agency) will give you an answer other than to wait 24 hours before diving ... which is the end result of this answer too. Are you asking about DCI from simply working in a mine and then exiting the mine, or is the question that you work in a mine and then sometime after work you perform a recreational dive at sea level? Assuming it is the latter, working in a mine before a dive needs to be accounted for. Also assuming no air is feed into the mine that might pressurize it any further, it appears the pressure at 3000' below the sea level would be about 16.44 psi - which is the same as being about 4' underwater. So working at 3000' is the same as being at 4' underwater for hours and is essentially a saturation dive to 4'. Diving immediately after such an exposure needs to be accounted for. Unfortunately recreational dive tables are not set up to account for a dive after such an exposure since the dive is essentially a repetitive dive now after a 4' saturation dive. Four feet may not sound like much, but the maximum depth that can be dived to with no time limit and then surface without getting DCI (known as the Minimum Bends Depth) is believed to be approximately 20 feet. So a 4 foot saturation dive is in fact a significant exposure and it will affect repetitive dives even though the 4' exposure itself will not result in DCI. So the answer to your question would depend on how long you are exposed to that increased atmospheric pressure in the mine and for how many days at a time. It would seem that the best solution is to wait at least 24 hours after exiting the mine before diving. The problem is not that you cannot dive right after exiting the mine, but instead that the tables are not designed to calculate times limits after such an exposure. The current U.S. Navy procedure would allow you to dive to 20 feet (since there is no time limit at 20 and shallower), but if you want to dive deeper than 20' then the Navy procedure is to wait at least 18 hours. However 24 hours is more conservative and prudent.

Another approach would be to use the same procedure altitude divers use when they ascend in altitude before a dive such as ascending from sea level to a dive site elevation of 3000' (which is exactly the situation you are encountering). The procedures used vary depending on which dive table is used, but when using PADI's RDP you would treat yourself as arriving with an "F" pressure group and if using the U.S. Navy table I would recommend that a minimum repetitive group designation of "C" based on my altitude research (the Navy says "B"). Another altitude procedure that is used when ascending in altitude before a dive is to treat the dive as though it were 10' deeper than it really was - which appears to work well.