FFM removal skill gone bad...
A little self disclosure here to stress the importance of practice, even for those little used skills. After practicing this complex skill in the pool and feeling confident about it, I jacked it up pretty good on a skills dive. We SCRUBS often do two dives in a day; the first dive being a wreck dive with decompression, and the second dive being a shallow reef drift dive that some of us use for skills practice. Here's the days events...
I had a series of equipment problems yesterday leading up to the dive, and then during the second dive, while 'practicing' a complicated skill, I screwed up and it turned into a thumbed dive for me. I'll explain:
I've had a pesky number 2 AI cell that was getting voted out after about an hour underwater on previous dives. I put all my cells on the Narced @ 90 tester located at Fill Express in Pompano Beach (Thanks go out to Mark for providing this free of charge diagnostics tool!). The number two checked out fine on the test showing a nice linear profile and expected tolerances. I decided to buy a spare for my kit, just in case it crapped out. It would come in handy yesterday. First, I setup and calibrated my head unit the day prior to the dive. All 3 cells calibrated fine, and I packed my kit for yesterdays dive. I turned the unit on after loading it on the boat, and the number two was reading .21 in air. On the ride out, I decided to finish my predive checklist and prebreathe the unit. I switched the injection from manual to a setpoint of .4 and started to breath the loop. The number 2 went to zero. It had completely died. I luckily had the spare, and I completed a cell swap and recalibration during the ride out to the wreck. The new cell performed flawlessly on the dives.
Prior to splash on the first dive, I heard hissing coming from my bailout 1st stage. I had checked the pressure on the tank the night before and not seen any problems with the regulator. Now, it was leaking gas, and it turned out to be a crimped o-ring on a LP hose used for a whip to my BOV. While kitted up and ready to spash, I took the reg off the bottle, removed the hose, inspected the o-ring, and reassembled everything. Problem solved. My compradres were starting to wonder if I was jinxed and whether they should dive around me! :o
You know how things happen in threes? Well, the first dive was spectacular, other than a slight hiccup in stowing the grapnel for drift deco. The second dive would turn out to be a little different for me.
I had planned on doing a FFM removal exercise on the second dive. This is a fairly complex and task loaded event, so practice is important. The Drager has a mouth bite, so even during a flood, the loop stays closed. The only two reasons to ever really remove it and don a half mask are for complete catastrophic flood where vision is hindered, or a caustic cocktail that has contaminated the mask or mouth bite. Here are the steps I briefed prior to splash to my buddy (padipro) and the videographer (netmage).
1. Identify the need to remove mask
2. Bail out to BOV
3. Retrieve spare half mask from pocket
4. Verify offboard tank pressure and deploy 2nd stage regulator/purge
5. Shutoff BOV/nasal reg gas supply from offboard bailout tank
6. Remove FFM
7. 2nd stage in mouth/purge/breathe
8. Don half mask and clear
Well, I f'd up and forgot to do step 5. Guess what happened? I got a massive free flow from both the BOV and nasal second stage in the FFM. I donned the OC second and half mask and finally got the freeflow stopped with the help of padipro. I had lost much of my OC gas supply and ascended with my buddy after giving him the OOA signal and thumbing the dive. Scott deployed his offboard regulator and had it ready to donate if was needed. I surfaced with about 400 psi. Stupid mistake. I'm headed out this afternoon to do the same drill again in 20 fsw instead of 70.
Thanks to Scott for the help! He's a great buddy. Once I was on the boat, he descended again down the drift bouy to join the rest of the group whom I'm sure were either laughing at me or shaking their heads! :o
All in all, the first dive was great and the second dive was a learning experience. Practice makes perfect if it doesn't kill you first!
I posted this here so that those looking to transition to a FFM take the skills and practice needed to be proficient seriously. You don't really need to take a class, but you need to think through the skills and contingencies needed in the event of something goes wrong. Plumbing and familiarity are important, and can mean the difference between lost gas and a fumbled procedure.
Hope this sheds some light, and practice, practice, practice!