Flatliner
It was the last diving day of the Red Sea live-aboard holiday in November 2006 and we had the prospect of two reasonably tame dives in a little cove with a reef before we washed the gear off, stowed it away and adjourned to a hotel for our off-gassing day before the flight home.
'Reasonably tame' quite suited me as it hadn't been quite my week. It was the first time I had taken the rebreather somewhere warm and the first time I'd dived it in the wet suit and I wasn't doing it well. I had a bunch of rather jagged profiles in the log but it was getting better. I could see me remastering CCR buoyancy just in time to go home which was a little frustrating as in a dry suit I can stay just where I want.

The Zodiac dropped us at the designated spot and we dropped onto the reef and started off in the recommended direction. I was running a fill of DragerSorb because that is all they had on the boat and I had been warned it would only give two thirds the life of my usual Sofnolime but the temp stick in my Vision electronics (an upgrade that I got in February this year (2006) to my faithful old 2001 Inspiration) was telling me I had quite a lot of life left.

I had prebreathed it and the dark (warm) band on the scrubber display was showing the reaction starting at half way and that it had not yet warmed the rest of the fill above there when we dropped in. It wasn't a particularly interesting dive. I'm not really into fish and weed even if they are very big fish (sharks) and very pretty weed (coral) but I quite enjoy just being in the water even after all these years. For once this trip the buoyancy is tame as can be. I'm running the standard set-points and switched both the Vision and the VR3 up to 1.3 and with the sand shallower than 20m this was a no stop dive.

I specifically remember noticing the next black block vanish from the temp stick display so it was now less than half but one of my colleagues on the boat had run right down to the scrubber warning a day or so earlier. I checked the contents gauges and I gave 120bar of O2 (well 96% by the boats meter) and have 170bar of Air DIL. We are officially diving in a three - myself, one of the guys from the club and one of the boat guides and we are getting strung out.

It is about 12 minutes into the dive and I make a handset check and the scrubber display has become a line of dashes. I don't like this. I seriously don't like it. The ppO2s all look OK and I really doubt that the scrubber has suddenly exhausted itself but I've had one run in with CO2 and I am not going to have a second. I will admit that I wondered about continuing the dive and monitoring my breathing rate but discretion won over and I turned the switch on my Bob Howell BOV and was breathing the DIL OC. I suspect I am here writing this now because of that decision.

I look round. Dougie is pushing on into the distance and Joe, having solved a problem for another of the guests is following up. I signal ME PROBLEM UP BYE-BYE OK. I don't think he liked it but on a rebreather the rule is if in doubt bail out not look after your guide. It wasn't the slowest ascent but it was hardly a high risk profile.

Karin, one of the guides, is in the Zodiac that picks me up and they take the weight belt from me and haul the Rebreather over the side. I clamber after it, close the valves and shut it down. They start the run back to drop me as they are not expecting anybody else to surface for at least half an hour. The rebreather is beeping. I'm perplexed but I shut it down. Moments later it is beeping again. I carefully, deliberately step through the power down, watch and wait and it restarts. Ominously the ppO2 values are unchanged.

Back on the boat I pull it apart, take out the canister, remove the head, take up my camera and take its picture. Remember this is now naked cells on the work bench. I am horrified. I nearly made the decision to continue the dive based on those ppO2 displays and they are frozen. Was the solenoid open or shut? I suspect shut but I dumped the counterlungs on the way up and shut off the gas valves in the RIB so I can't remember any definite fact to prove either way. Were the computers controlling the ppO2? I can't tell. Do I feel lucky to be alive? You bet.

I had to pull the batteries to get control back and then I dumped out the dive logs onto the laptop. For anybody who has the APD software here is the CCL file for the dive and for those that don't here is the printed version as a PDF. You can see the scrubber and the ppO2 values tracking right up to a point then the lines go flat. There is a three minute period between 11.50 dive time where the traces stop and 14.50 dive time where I started to ascend some of which I was on OC signalling to Joe.

OK. I'm writing the first draft of this in my room at the Coal Beach at Marsa Alam and the head will obviously go back to APD and hopefully they will find a fault and fix it but I can't help wondering about the what if's of this. Would I have noticed the displays had frozen if the scrubber had frozen too?
The best news, of course, would be that the problems were all in the displays and the controllers were still in control but I suspect that my long term aversion to the fourth cell systems has broken. I still rate wiring one cell into a deco computer and using that to plan deco on as daft but having one giving a check number with hi/low beep warnings suddenly feels like a life expectancy enhancement.

More details when the head comes back.
Well I arrived home in the early hours of Thursday, I posted the head to APD on the Friday and according to their notes they received it on Monday. By the next Friday it was back with me. The Maintenance form said:
SUPPLIED NEW LID/HANDSET
WITH ORIGINAL CELLS AND SOLENOID
OLD UNIT RETAINED FOR FURTHER
R&D TEST AND INSPECTION
So I have my new cells that I bought a couple of weeks ago and my old solenoid with all new electronics, housings and wiring. They also replaced with new the cell that failed on me just prior to the trip all F.O.C.

OK I'd have liked some more details but they probably didn't have any yet and they sent me a new unit so I can go on diving. I'm happy with that. If it was my product I'd swap it out but then we have things on the shelf ready to ship and APD have a waiting list.
I hope that later on we will find out what happened. It may well be something trivial like a broken signal wire but I would prefer blank displays to wrong displays - it just grabs your attention more.
Then, just before the new year 2007, Tino de Rijk, an experienced, dutch trimix CCR instructor obtained a set of details from the factory which he posted to the Rebreather World Forums. This is copied to A closer look at Vision on therebreathersite.nl. Clearly APD have addressed the problems of data loss in both directions, which is comforting, so I will look forward to the next release of the software.

So what have I done in the meantime?
Well the main thing was that after years of being rude about them I bought the fourth port system for the Vision from Narked at 90. I am aiming to run this into the VR3 as a display only system and, as I wanted a ppO2 meter on the IDA64, I have obtained the p-port kit for that also.

I'll add that to the modifications pages when I get it installed.

05/02/2007 Fourth Cell system installed.
15/04/2007 New software installed.
Lots of diving...