This past weekend (June 27-28th), I was in Tobermory, Ontario (Canada) for some fun diving as well as for some courses that I was team teaching (AOW, Bouyancy, and Night). The courses and other diving was scheduled for the weekend proper so when we arrived on the Friday we had made plans to take a tour of the local recompression chamber facility which included a "dive" in the chamber. Cost was $20 per person and we were limited to 6 participants (there was also a tender that came on the "dive" with us).
Prior to us getting there the technicians had pre-dove the main chamber since it takes more air and thus more time to take the main chamber to the depth. The plan was to have us cram into the air-lock and then take that to depth at which point we would move into the main chamber. Planned depth was maximum 135' and we were allowed to bring our computers in with us (they had a bucket of water to put them in).
They gave us a thurough breifing on the facility as well as health considerations that we should be aware of. We were also told that equializing inside the chamber was just as important as when diving but could be more difficult with it being likely we would have to equalize close to 30 times for the first 10'. After which we would descend faster but the equalizing would be more natural.
Step 1 - empty pockets of anything electronic (cell phones, watches), take off shoes and then cram into the air lock. I do mean - cram. I can't begin to explain how tight we were but I'm sure to an outsider looking in ... would get the imprssion of a bunch of college kids trying to see how many would fit in a VW bug.
Step 2 - descend to 10'. Lots of equalizing and we started to feel the first effect of Charles' Law. I'm sure everyone has noticed the increased temperature of their tanks if they get too fast of a fill. Well it apparently happens inside a chamber as well.
Step 3 - once everyone was comfortable at 10' we began the descent to 135'. Much quicker and equalizing was going good for everyone. I was concentrating on my equalizing and the effects of Charles Law was definitely present as everyone was sweating pretty good.
Step 4 - there wasn't a depth guage inside the air lock but best bet (based on how long it took us to get to that point and then to the rest of the way to 135') was around 90' the individual sitting directly across from me decided that my concentration on equalizing was rather humorous and he started to laugh. Well this set off a chain reaction and within 5 secs, we were all killing ourselves with our laughter. This started at 90' and was affecting all of us. Afterwards it amazed me to look back and see the effects.
Step 5 - at around 115' either the perception of or our actual voices changed. It sounded like we were a bunch of chipmunks on helium. Of course this didn't help to resolve the laughing and only made things worse.
Step 6 - when we got to 135', the door to the main chamber opened up and we were all able to crawl in (still laughing of course). Waiting there were several different tests for us to allow us to feel the effects of the narcosis (as if it wasn't apparent to us already). The tests include moving ball bearings with tweezers, combination locks and my personal favorite ... a Dr. Seuse book (Fox and Socks - I think it was Dr. Seuse). We spent 10 mins at this depth and laughing the entire time.
Step 7 - we started to ascend, they took us up at 60 fpm and our first stop was at 30' for 1 minute, follwed by 20' for 3 minutes, then 10' for 7 mins and finally 5' for 10 mins. I think this was the schedule - I may be mistaken. During the ascent we got to experience Charles' Law in the opposite direction with the temperature quickly dropping and actually below the dew point so we had extremely thick "fog" develop inside the chamber.
All in all, it was a very unique experience and it has made me rethink my belief that I don't start to suffer narcosis until 120' or so. I had experienced it occasionally shallower then that but nothing to the extent that I did through this route.
