Normoxic Trimix Rebreather Training

What and Why?
Rebreather training comes in stages. You start at level one known as Mod 1 (Module 1 probably, I never asked). Mod 1 teaches you the basics of rebreathering such as cleaning and maintaining it so it doesn't go wrong and diving skills which contain, naturally enough, what to do if it does go wrong. It is the OW and AOW of rebreather diving.

Once you have mod 1 you can go and dive and build up some experience of the thing. My TDI card certified me to use air as a diluent (the basic gas in the loop to which controlled amounts of Oxygen will be added), a maximum depth of 40 meters and decompression stops not exceeding 5 minutes.

Mod 2 is the short hand for the second level training option on a rebreather. This includes much more serious decompression stops and the use of Normoxic Trimix as a diluent.

If you want a discussion of Trimix follow the link.

Now it is always said that you don't chose the agency you choose the instructor but there is only one agency that offers the course I wanted so the instructor was the only choice. I was pointed to Martin Robson of Eau2 who are based at Runnemead Divers. Martin is a time served technical instructor with an international training schedule and is right up the tree in the IANTD so he seemed a very good choice. My advice was that he teaches technical skills rather than just examines them. The web site also said they had taught just the course I wanted in Lanzarote in the Canaries in the spring of last year.

Now those of you who dive the UK will know that getting blown out is a feature of our diving. So booking a week off for a course and then sitting on the dock watching the waves smash against the shore is bad news. Much of my initial, mod 1, course was transported from Plymouth to Stoney Cove as the weather took advantage of my natural tendency to seasickness to ruin the first attempt. Lanzarote might be the Costa Club to some people but the relatively benign climate and the fact that it is the peak of an undersea volcano, meaning that you can have whatever depth you want by just swimming out further, make it a very handy place for a deep water course.


Right Let's get on with the story
We had 20 Kilos of baggage allowance and Britannia kindly give you an extra 5 Kilos if you are a diver but Martin warned us to purchase another 10Kilos at 35. Once I started packing this fell apart on me and I phoned for an extra 30 Kilos on top of that. I just about squeezed into 65 Kilos and a 5 Kilo cabin baggage allowance. Once we were passed check-in the flight was quite uneventful.

The Hotel is a strange place to English eyes. About 40 living room, bed room, bath room apartments with a balcony gathered round a bar and a swimming pool. We just had two as Martin is trying to provide a course at a reasonable cost. Martin, Paul and Steve had one apartment and Danny, Emma and I had the other. There is a zip-bed folded up in the bedroom but I just put the sheets, pillow and blanket on the living room sofa. The room was already full of rebreathers in various states of disassembly so to add the bed to the equation would have been silly.
We investigate the little self service shop over the road for breakfasty and lunch shaped things and flagons of bottled water. We sleep OK although I am not too keen on sharing the room with the with the fridge and Kareoke night at the bar starting when I was planning on going to bed did give me emotional problems but it didn't go on too late.
Next morning we piled into the van and headed off to the dive shop to pick up the hired cylinders, weights and fill with Sofnoline. This was Deco-stop Diving, now gone, in Costa Tequise and aside from one dodgy fill that we picked up analysing they were cheerful and helpful even bringing stuff to us and finding things to lend/hire as we progressively broke every bit of diving equipment on the island.


Then it was off down to our dive site from the week. We are shore diving because the place is suited to it. Remember we are on the top of a volcano several hundred miles off the coast of West Africa. It rises from the seabed as a volcano shaped cone so you can have virtually any depth you want by just swimming out further. We have the steps on the jetty to enter and exit on and we can dive on virtually any state of the tide.


Martin walked us out on the rocks to point out the salient features of the area and, to cut a long story short, dropped the car keys. Now when you are climbing over boulders with an average size of half a meter to a meter in most directions this gives something small like car keys an opportunity to rattle down a long way. In hind sight it was a serious problem solving, team building exercise and the final solution of Steve upside down in one adjacent but slightly larger hole poking a piece of rod we borrowed from the local dive shop through into the hole the keys were in was a solution. The day was saved. Time to kit up.

Thursday Dive 1 - 23 meters 67 mins
Sorry. No in water shots. I don't even ask if I can take the camera on training dives. Danny started well discovering that the boot was virtually falling off his suit so he wasn't diving.
We ran down the slope and the flash cards started to make their appearance. I have to agree that flashcards are a very good way to run a course like this but being hit by a card saying 'Low O2' makes you have to react quickly and it soon showed up the weaknesses in my disaster recovery drills. Back in the shallows Martin laid out a line and we started eyes closed drills. Drop the bailout cylinder and clip it to the line, continue up the line until patted on the head, turn round and find your tank and clip it back on. Somebody had parked another tank there but it wasn't clipped on so it wasn't mine.

Thursday Dive 2 - 7 meters 35 minutes
This was a six meter dive in full deep water kit. Danny had managed to hire a wet suit and the tiniest pair of fins ever. Martin ran him through some of our drills from the morning then set to run a line and do some out of air style drills. There is a lot of swimming about with your eyes shut and air sharing stuff. Now my TDI mod 1 course mostly concentrated on managing problems yourself but here we were to learn the essentials of using your buddy and being a buddy. Remember the amount of gas to bail out from 60m is truly jaw dropping so the team carry enough to get one and a half divers out.
The drill evolved simulating an out of air by switching off the loop and onto the bailout OC reg, swim to your buddy, locate and take his bailout and breathe that. Switching to the OC reg means that Martin can spot you cheating and taking a sneaky breath which, if you were on the rebreather would be impossible. Thus dive must go down as the 'Fry Dive' as most of the drills were performed in a cloud of immature fishlets.

Friday Dive 3 - 45 meters 96 minutes
Our first planned deco dive. 45m 20mins 27m for 2/31min, 18m 2/35min, 12m 2/38mins, and 6m 11/50mins. I switched up the setpoint too early and had a quite nasty oxygen spike. What I should have done was stayed on 0.7 and let the spike effect push me up towards the 1.3bar. At 45m we ran some drills involving attaching and removing the bail out via the 'offboard' hose both to ourselves and a buddy. The flash card made it's appearance again mid way through the agreed drill. I'm still over weight and it was running me ragged so I trashed my way through the whole Argon bottle and had to revert to using the wing. This was new to me so I naturally made a pigs ear of it. Once we had completed the deco Martin had some more drills.
Drill one. Switch to the bailout so Martin can see bubbles to know if we are cheating then eyes shut start two divers at opposite ends of a line and without breathing swim towards one another. On meeting locate their reg (clue: it's in their mouth) and swap regs. Once you are on their reg you are allowed to breathe. Next, eyes still closed, swap the bailout cylinders. Now I was quite pleased to manage to identify that the way we swapped regs linked the hoses through one another and I had to take the reg out to fix it and then hitch up Steve's tank but Steve accused me of closing his dump valve and inflating his suit. Strange. I know that I handled him very gently as I was worried about dislodging his mask. However it occurs to me that a certain Robson was close on the fray and Steve is trained by him. Not that I wish to make accusations, but Steve, it wasn't me.
Drill two On the same line take your mask off and swim the line and at the far end turn round and swim back. It was about half a kilometre each way I think. I had heard that these cavers carry big reels and now I know. I hate mask off drills. The one thing the PADI Tec Deep course instilled in me was always carry a spare mask.

Saturday started with Danny tearing the neck seal of the hired drysuit. As Paul had an ear discharge he wasn't diving and he is a big lad so they fetched his suit and put Danny in that. Anybody who knows Danny will now realise that Paul is not a little guy.

Saterday Dive Four - 52 meters 70 minutes
Fifty three meters and we are going to do a simulated total rebreather failure of one diver and some added tricks like manually driving the unit and boosting the ppO2 on deco. We made our way out and down and were put onto manual control as expected. Then suddenly Danny is on his bail out reg and signalling UP with urgency. I confess it took me a moment or two to realise that Martin had picked him and we were combining two drills. Back the way we had come pushing in the stops. Then came the signal to swap my bail out with Danny. He has, simulatedly, breathed half his Trimix bailout and it is time for me to pass over my more full tank. He takes my bailout reg and then I unship the tank and pass it over. The diver with a problem gets the team's gas but each team member needs to have gas in case he runs into his own problem. The rule is to breathe half of what you have then swap. Once Danny is established on the new bailout the simulation allows him to swap back on the loop or the low ppO2 of the bailout (breathable at max depth) would keep him in the water forever (yes - we do have the times for that on our slates). Then comes the DSMB drill. Heck my DSMB has been out so many times it can virtually do it itself and Danny is the same. The 90 seconds course standard is no problem. Then Steve gets told that Danny needs another tank swap and the DSMBs certainly complicate matters.
We end up at 6m with an 18 minute stop to do and we are told to boost the system to 1.4 bar. Martin is circulating noting numbers so the debrief will be embarrassing.

On the swim in I developed calf cramp so I cried out of the rescue drills. This is the old routine we learnt at Rescue Diver to recover and dekit a non-breathing diver at the surface doing AV as you take off the rebreather so a boat crew etc. have a chance of pulling them out. I was annoyed with myself as although I'm quite a bit older and a far weaker diver than the others I hadn't missed anything up to then. However I was no longer a sensible person to be in the water so it has to be.

Three days done. That's half way through the course. The news from home isn't good. My son, my mother and my aunt who is visiting have locked themselves out. I advise them to go for the cellar door window as it will be the cheapest to fix. Cheap is a relative word here. **sigh**

Sunday Dive Five - 60 meters 94 minutes
This is the defining dive of the course. 60 meters planned depth. Not 61 Martin is careful to point out. I have knocked off another two kilos and am diving the suit on desqueeze and wing for buoyancy. It's like the old twinset. We are to leave the rig on the low set point and drive the loop ppO2 to 1.3 from our usual switch up point at about 30 meters. Martin also wants us to trade the diluent inject hose to our offboard bail out so we use some of that to stretch our diluent out and use more of the 7 litre tank as it is paid for. The descent goes well but on hitting target depth, I put 59.2 meters on the Uwatec Dtimer and 58 meters on the VR3, I get a cell error. I was annoyed. Put it in context. I have a failure in the sensing part of my rebreather, one of the sensors is reading 0.15 bar different from the others and my time to surface is about 40 minutes.
Martin picks up that I should have done a more vigorous diluent flush but very forgivingly puts me back on high setpoint and leaves me out of some of the drills as I am in a real error mode. We do our stops back to 6m and here Martin has us deploy the DSMBs and do a boost to 1.4bar ppO2. We stretch this stop and then swim back. On reaching the steps I am showing just under 20bar of O2 and the cramp has returned. I crawl back up the steps.
Sitting on the wall for a few minutes refreshes me enough to dekit. Martin and the others arrive and talk is, amongst other things, of cell errors. Martin starts to demonstrate a calibration check but runs my rig, now showing 15 bar, right out of oxygen. At this point I discover my O2 SPG 'zeros' at 10 bar displayed. This means I entered the water for a 60 meter dive with 90 bar of O2, did all manner of O2 based drills and exited the water with 5 bar. **Expletive deleted**

It's Monday morning. It's 19°C and I'm cold. I am also so looking forward to not sharing my sleeping accommodation with a refrigerator.

Monday Dive Six - 53 meters 78 minutes
Monday we had to go back to the dive shop for fills and new Sofnoline and then sat down to plan the dive. The idea was to find the Blue Hole at 18m and dive through that. (Does every dive destination on earth have a place they call the Blue Hole or is it just most?). The plan was to do an 18m search, find it, down through it, out the bottom and then down to 52m, skills and the ascent.
However on arriving on site I did my usual trick of kitting up early and sitting on the dock chilling out so I missed the girl from Deep Stop Diving warning Martin that there was a serious current running and they revised to plan B. The dive was reasonably uneventful, it was the first time I had done an ascent on OC where you have to vent the loop by flashing the mouthpiece open over your head, but I scared myself slightly when the new even lower weight me had a bit of a suit runaway and Martin grabbed me to re-establish the stop depth. He now has me down to 9Kilos of lead plus the 7L steel stage. When you consider that I finished my mod 1 course carrying 11.5Kilos in the fresh water of Stoney Cove this is a serious drop.

We finished the dive by redoing the rescue scenario of unresponsive diver in the water so dekit, ventilate and tow in.

I am so tired now. We have already done 7 hours and 20 minutes under the water time plus swim outs and surface stuff. I would have passed on a couple of dives by now if this had been a holiday. However this is the last day diving. We fly at five tomorrow evening. Martin is trying to pace the theory side so that we get tomorrow free(ish). Most people want to do something interesting but I will settle for a veg out by the pool day.

Tuesday Dive Seven - 40 meters 60 minutes
I don't remember much about this one but it ended on the beach not at the pier after a protracted manual control (solenoid jam open I think). I'm writing this one up weeks later. The main thing I remember is how far it was from the exit point to the van. Clearly the only way to do this sort of diving is from a hard boat with a lift.

Now the bad news. "You haven't failed. You just haven't passed yet."
Fair deal. I've been reducing the weight I carry all week and my buoyancy control has gone from awful via bad to poor. Martin wants to see that sharpened up quite a bit. Bad buoyancy control technical diving is messing about with the most fundamental thing - how deep you are. You must have that under control doing stops. Two more dives in the UK. There is a possibility of a south coast trip or maybe Dorothea Quarry in North Wales.

Saterday Dive Eight - 46 meters - 59 minutes
Well here we are at Chepstow and the NDC for a weekend. I have a both good and bad connections with Chepstow. Firstly that my daughter and granddaughter live very close at hand so I can go and stay, which is fun, but also I had a very bad experience here diving OC when on a trivial 30 meter dive I turned into the gas guzzling monster who could not get enough gas through a TX50. I don't want a repeat of that.
I am sharing Martin with two OC Trimix students who have some primary drills to get through while I, certainly for the first dive, just need to do the routine procedures. We cut an OC shaped table and, as I will be breathing a richer mix I just check it is inside what I calculate.
There are some simple problems but I'm in my new Otter Britannic suit and it just works. Weighting is right so buoyancy is right. Nice horizontal position in the water. OK I admit to more than a bit of trepidation as we left the shot at 46 meters and as my breathing rate climbed a bit I deliberately went round the gauges and reassured myself I has lots of gas, spot on ppO2 and was OK. Once we were underway it was pretty smooth. Martin made us stay an extra 5 minutes at 6 meters but it was warm and even sunny, just beginning to get boring.

Sunday Dive Nine - 50 meters - 57 minutes
More of the same. OK this time I am to do manual oxygen control on the descent and I spiked it a bit and fussed about but 1.4 isn't really a problem unless you stay there and are doing a long dive. I was more worried about Martin catching me out with a high ppO2.
The only complication was the we drifted under the pontoon while doing our 6m stop. Well no. Martin pointed out we were finning which is naughty. We weren't quite trimmed out and we were kicking slightly to stay level. Oh well. It must have been better because he shook my hand and passed me with a set of strong advice to practice the skills.

Overall a fantastic course. It has changed the way I dive the rebreather quite fundamentally. It has sadly reaffirmed my feeling that I am actually not a very skilful diver and I will have to make up for this with practice, practice, practice. Still. If that means I need to spend more time in the water who am I to argue?


Finally all the left over pictures.
The ones I'm not sure which dive they go with. Including Steve's very soggy scrubber - it still dived OK so we were quite surprised how much water came out. Even some of me shot by Paul Porter. (Thanks Paul.)


The pictures can be accessed by clicking the thumbnail but they tend to be 900K+ files
Pictures by Nigel Hewitt and Paul Porter.
Thumbnails by Easy Thumbnails