Out diving with the Dolphin on Sunday in the Firth of Forth, had one nice 51min dive in company of an inspiration diver and a pleasant lunch / surface interval. Decided to change from 40% jet to the 50% as my PPO2 was a bit *too* high on the first dive. (40% in the bottle)
Changed nozzle and did pos and neg pressure test. All good. Thought "I really must open up the OPV a little for the next dive".
For a variety of reasons I was buddied on the next dive by a BSAC Dive Leader who hadn't dived with a Rebreather diver before.
I gave him a heads up on the major differences and we kitted up and did a buddy check. Pre-breathe felt good and just before we dropped in I remembered the OPV. Asked him to open it up all the way. He reached behind me and said "which way to open it?" I said anti-clockwise and he then said "It's a bit stiff" "Nah that's better, how far open?" I said to the stop, he said "It just keeps turning", I got the Inspiration diver to check the valve and they confirmed it was already fully open...
So we rolled in... dropped down a couple of metres and I did my 360 for the bubble check, as I was doing this I thought I felt bubbles behind me, I gave buddy an "OK?" and got back an unsure OK.. I'm now concerned so I check my PPO2 and contents, both are ok, I'm just looking back up at buddy when I exhale and there are a mass of bubbles behind me, tongue in the way of the mouthpiece and I'm giving him "Problem, Go Up" as I reach for the bailout.
Surfaced fine and once the boat was there I sent him down with the other OC divers and checked the set.
Guess what...? He'd managed to unscrew the OPV from the bag by almost two whole turns...
Lessons (although I'm sure we all know most of them!):
The breathe felt fine even when the loop was filling with sea water (I poured water out of the bags, the scrubber and the loop once I got home, and I don't mean a dribble, it was sloshing in the scrubber!)
Bubble check is critical.
"If in doubt, bail out" is the best advice I've ever had.
Don't trust a non Rebreather diver to do *ANYTHING* to your kit/set, no matter how basic (It's a dump valve FFS!)
Oxygen sensors don't like seawater
(UWATEC Oxy2, collected that morning, had just been fitted to check how it affected hose length etc! crap crap crap!)
Buoyancy was affected surprisingly little given the quantity of water in the set, certainly not enough to be obvious.
Feel free to add anything I've missed!
Stay safe out there!
Smudge
