Nigel and the Inspiration
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This is the old page (2001-2006). For my new Inspiration writeup see here.

This started as a report, back in the days when CCRs were relatively uncommon, and has developed, since 2001 when I started, into what is now rather a blog of modifications and changes. Some of the descriptions are now getting a bit out of date but the modifications don't make sense without the early stuff on the Classic.

For a basic explanation of Scuba rebreathers see here and for the article I wrote for the Sussex Diving Club magazine see here.
If you are diving in normal scuba gear and you are buddied with a rebreather diver here is what you need to know.
If you want detailed details see the official manual.

O2 reg   ADV   Argon   DSV   Torch   Vision electronics   Removable lungs   CD handle   4th Cell   Stages   Tools
Picture: Simon Kay 2007 I purchased an APD Inspiration Rebreather in 2001. It had its good points and its bad points so I discuss some here. Actually it's very difficult to comment fairly at times. There are bits I'm not happy with but conversely APV/APD are just the people to deal with. Their attitude to customer service makes them my preferred supplier regardless of the idiosyncrasies of the unit. I would not want to be using dive kit like this without people on the other end of the phone who want to help.

I will run over some of the features of the item as I bought it and as I saw it as a novice rebreather diver. Take it as just that. I have changed a few of my ideas in some areas since then but I am not a novice engineer.

When you start rebreather diving you are warned that you are beginning again and that is really how it is. You have much to unlearn and even after many dives and now with a growing familiarity with the unit I still keep discovering things where what I used to do is now wrong and skills that I once learned slowly that are now useless, even embarrassing. <sigh>
This is the original computer handset (see later for the update). There are two of them. They're a bit simplistic but when operating them in gloves in the cold they are reasonably chunky and you get what you ask for. The trick is that the first one to come online is the master and runs things. They both monitor and display the three oxygen sensors and if the master quits the slave takes over at once.
The switch at the bottom is power on off and the three buttons are sliders that move about half a centimetre and, I believe, sweep magnets over sensors to reach inside the sealed case. These seem to be a running fault as everybody seems to have their own tricks to get a sluggish switch to work.
Don't think "Computer? Like my dive computer that reads my depth and time and plans deco for me?" These are simple voltmeters to read the oxygen sensors and present it as a partial pressure reading with a control loop to drive the solenoid to add extra oxygen when it is below a preset level.
They certainly were not designed by instrument makers but I suppose I'm not a scuba equipment manufacturer so I shouldn't complain too loudly. They perform well maintaining the loop ppO2 quite accurately even when I was going through the beginner phase of relearning buoyancy control.
Classic handset
AutoAir AutoAir This is the wing inflator and fallback reg so you can breathe the diluent tank if it all goes pear shaped. Currently I think it sucks. Every unit I have dived (all 3) needs treating nicely or it free flows - even my brand new one - and it has too many buttons. However other people with far more experience of the unit than I have seem to tolerate them so maybe I'm being too picky. I added the whistle because one has saved my bacon in the past but it has to be the Buddy part as the connector is a weirdo, like nothing like anything else I have seen.

I stripped it and screwed the adjustment up a bit tighter after it free-flowed on me inflating a blob. The only fix at the time was to shut off the DIL, complete my stops and reopen it to surface when I needed it to inflate the wing.
This is the original mouth piece. If you hold the black bits and turn the white bit so the mouthpiece points down you close off the opening. This is needed so you can take the thing out of your mouth without allowing water to run back into it. This would at worst flood the loop so you can no longer breathe from it and make you several kilograms extra negatively buoyant or at minimum sentence you to a dive with gurglly sound effects. The stories I hear from when people have failed to do this seem to indicate that the design of the unit successfully keeps water from the important bits.

I tried to change the jaw-breaking mouthpiece supplied for a more comfortable Scubapro one but the fitting is bigger and it split. After a while you just get used to it...
Oxygen Inject
Diluent inject
At the bottom of both counterlungs are the injectors. The left hand counterlung (right hand image) is equipped to inject the diluent, air to newbies like me, and the other one injects oxygen. They both have a gauge so you can monitor the contents of the tanks.

You need the injectors for the manual control of the unit. You add diluent on the descent to make up for the loss of gas volume as the pressure increases and the oxygen injector enables you to drive the system yourself if the inject solenoid quits.

You can see that my unit has a plate to fit an alternate injector. This allows you to carry two diluent mixes. Admittedly people who dive sophisticated mixes don't seem to have one but if I like it I have it.
Since taking these pictures I have rearranged the gauges to run down the inside edges of the counterlungs. This makes them more intuitive to get my hands on them. There is an incredible amount of Velcro and stitched channelling on the counterlungs, most of it is unused and much of it incomprehensible.
These are the T pieces on the shoulders of the counterlungs. They have blades inside to try to ensure that any liquid entering the loop is dumped into the right hand (exhale) counterlung. It's harmless there and you can drain it out after the dive. You use this mix of exhaled body fluids and other gunk to gross out the more squeamish team members.

This is the main dismantling point for the hoses so you can give it a good clean out with disinfectant. Since what you breathe out is going round and round this is considered a life expectancy issue as it could culture up some very interesting stuff.
CaseYeah I put my name on it. I don't like wearing brand names (except Honda who I owe) so the id is me. I had lots of these stickers to reletter the race bikes after the inevitable happened. I don't actually need it for identification as if you're diving with a couple of rebreather divers I'm the one with the yellow wings. (I hate that black on black look.). The fun is that I have once been recognised in the water by the name and a diver I had only ever exchanged internet forum postings with came over to introduce himself. After a few years the letters began to fall off so I have a more sea-proof set made by Divesigns.

Overall I'm not very impressed with the harness. It has too many clips, adjustments and fiddly bits. There are 6 clips to do up all with their own pull to tighten adjustments. What I need the D rings that are trapped between the wing and my shoulder blades for currently eludes me and why does the wing have a hole in it so you can fit a suicide bottle? Nostalgia? At least the collar for the bottle gives me somewhere to stow the reg on the 100% side. I added this as the manual gives bailout examples which call for breathing 100% shallow but I fitted an Apex sliding shut off valve, as recommended in the manual, to stop anybody making a big mistake deep.
These are the integrated weight pockets that I bought as an extra. I finally figured how they fit, it only took a couple of months, they might work a bit better now. The trick it to zip-tie them to the matching bands under the back plate. If you don't do that the moment you try to pick the unit up they drag forwards, pulling over the vertical strap they locate around and getting horribly knotted up. The other thing you can do is run an awl through the Velcro and zip-tie the bottom shut. I don't do dumpable weights as I consider that, as yet, I'm too young to die.
I need 12Kgs in a dry suit in fresh water and 15Kgs in the sea. This pretty much matches my 12L single rig which is rather sad. It renders the total Inspiration very heavy. I was hoping to shed some weight going from twin 300bar 10L tanks but it certainly doesn't feel like I have.
Weight pockets

Bolts Bolts This is a before and after picture of the bolts that hold clips that snap the back cover on. In picture one you will see the nuts and shaft that project into the body of the rebreather and scrape the paint off my tanks. In the second picture you will see what happens if you remove the screws and put them in the other way round. No gouge now? Well sorry no. My tanks are already gouged. But what the heck? These are only life support items made of steel that I will immerse regularly in sea-water. No. I'm not impressed. This is typical of the standard of the secondary engineering on the unit - it let down the excellence of the primary design but thankfully I notice they are gone on the current versions.
I wasn't too pleased when the lid of the scrubber came unglued. This is mission critical stuff. The scrubber seals with an O-ring that seats at the top of the inner canister so if that top leaks the dreaded CO2 can bypass the Sofnolime virtually scot free. Now as CO2 is getting a very bad press in rebreather circles at the moment that was a NO DIVE moment and as the dive was booked and confirmed for the next day I was significantly browned off. Oh well. At least it's APD who do turn round repairs fast unlike a lot of people in the dive business.
Carbon-dioxide at depth is not like carbon-dioxide on the surface. You don't just get breathless and tetchy - this is panic, tensed up, task locked and finally unconsciousness. You are warned to be seriously careful packing the scrubber with Sofnolime but this one isn't on the check list.
Scrubber lid
Battery case nut Similarly when the thread stripped on the 'nut' that holds the battery compartment lid on I was upset. Now I think I'm mechanically sensitive and I don't remember cross-threading it or being needlessly vigorous but it just let go. Fortunately it happened while I was sitting on the back of the car doing battery voltage checks not when I was doing a stride entry or something so it was just an annoyance. It was time to walk up to the chandlers and buy a stainless M8 nut and promise myself a rebuild in brass next time I was in the workshop. This little thing holds both batteries in place so it is a single failure that takes out both computers simultaneously so there would be nothing to warn you until you next look at the display and it's blank - grab for the other - it's blank too - DIL flush and bail out - clean underwear on the boat.

So, over all what do I think of the thing?
Well, despite the gripes I like it. I am prepared to believe that rebreathers are the future of diving but the Classic wasn't quite that rebreather yet. What would I like to change?
Harness improvements. It must be possible to make it simpler. You need to wash it so you take off all the hoses and clean them down in the sink and then it's time for the counterlungs. These were fitted with a sewing machine so it's time to fit screw on covers to the first stages and put the entire thing in the bath. This is silly so see the modifications section.
Better computer displays. The Classic was far too clunky and could do a better range of warnings. People have died because they didn't switch them on, which you must admit isn't APD's fault, but auto switch on when immersed is hardly complex electronics. Forgetting to switch up a set-point is also a serious problem and needs only a depth sensor (even just a pressure switch) to beep at you until you do something about it. The later Vision handset is much better.
The big breathing hose connectors catch you out as a novice as you can start to unscrew the wrong part and it is very hard to retighten them if you slacken it. On a unit this expensive any special tools required to fix basic problems should be in the box. It's only a bit of tube with some studs in it.
Perhaps a revised glue on the scrubber lid might be worth considering. I like solvent glues that effectively weld two pieces of plastic into one solid lump. They do cause distortion but that can be managed. Things don't fall apart then. Again I notice a design change on the Vision.
The AutoAir is a joke but it is so designed in that you are effectively stuck with it. I will very seriously look into fixing this with something that does not need babying and that is suitable to hand off. As it stands the Inspiration is effectively designed for solo diving. Its breathe-the-wing feature worries me. It will let you breathe in from the wing automatically if the tank runs out and then you exhale into the water. If you ever get to that point it means you have just discarded a lung full of buoyancy. I would far rather it went hard in my mouth and gave me the choice.
I was a little disappointed with the weight. With my additions it tips the scales at 30kgms but I suppose that is to be expected. This is including two 4Kg tanks, about 3Kgs of Sofnolime and a couple of kgs of gas. Then there are two first stages, gauges, computers, hosing and such. I expected it to be less but it's built to survive and I can't complain at that. Like all AP stuff it won't break with a bit of real world use.

Modifications and Add-ons
Oxygen regulator Oxygen regulator
Well the first fix is to look in the 2001 manual and see how it refers to breathing the oxygen on bail out. But how you ask? By fitting a regulator on the oxygen I suppose. That manual described it, although the idea seems to have gone out of fashion now, and it warns you to fit a slide valve to reduce the chance of anybody breathing this at depth with the obvious danger of an oxygen hit.

I used an Apeks TX40 because I've always found them simple, reliable regs and added the slide valve and a mouthpiece cover to make the point. It plumbs into the oxygen manifold and slips into the suicide bottle holder which is both out of the way and easy to reach underwater although, once you have pulled it out, it is impossible to put back in the water.

Now I have seen people with a similar rig and once saw the reg get trapped and freeflow in the water dumping a lot of the oxygen supply. Now you rarely check your contents gauges on a rebreather so this could be serious so I try to make the checks. Conversely having a pure oxygen regulator on hand paid off when some divers on a boat missed a lot of stops. The main offender got the boat's oxygen and his buddy got mine.

Bob-O-Matic The Bob-o-matic Auto Diluent Valve.
This is a wonderful thing. You don't need it but it's handy. On an Inspiration you need to make additions to the counterlungs on the descent and then fine tune your buoyancy by adding/loosing a little counterlung volume. Now the purists will argue that this is not minimum volume but it works for most of us but when I have my hands full of camera I hit a snag. The old open circuit way of trimming your buoyancy by holding just the right amount of breathe doesn't work any more. I can trim for down by exhaling through my nose but trim for up involves touching the diluent add button and I don't have a free hand.

The ADV is a conventional regulator that adds diluent to the loop if the pressure drops below ambient. On the descent it feeds more gas as the counterlungs compress as the pressure rises so I can still breathe in and when I am sighting the camera breathing in enough to just empty the lungs gives me that little puff of gas I need to trim upwards. Magic.
Bob Howell designed it, Oxycheq sells the body and you add parts from an Aqualung LPO and some other parts and it works beautifully.

APD now do one of their own and I might have bought that had I not been told that they were not doing one and that I didn't need one anyway by the people on the APD stand at a dive show. That was after I already had details of what it was like and I just wanted to know when it was due. APD do like to annoy me at times.

Now I set mine much looser than the APD one. It is set like a regulator so it feeds as soon as the loop bottoms out rather than making me suck for it. I can see the case for doing it the other way round but I have learnt to run minimum loop volume without needing the 'feel' of the lungs bottoming out.

Argon/Suit inflate tank A Metalsub clip and a 1.5L Argon bottle.
Now I commonly fill it with air but if I'm cutting a slightly exotic mix in the DIL I may not want to carry the Haskel to some dive site to top it up. So keeping the DIL usage down allows a simple air top to leave me a beneficially tweaked mix for the next day. Also there is the advantage that I now have two independent sources of buoyancy which may be significant one horrible day when I either break something or do something silly.

The system is finished off with an Apeks DST first stage with a Subaqua Products two way T swivel so it carries both the Apeks hose and the obligatory over-pressure valve so seepage or a full reg free-flow does not put the whole 200bar up the drysuit inflator valve with the obvious 'Polaris style' ascent consequences if my reflexes are not lightning fast.

The Metalsub bracket looks so much nicer than the bent stainless ones available and a couple of years seawater does not seem to have troubled the neat locking system. I bought another for the other side to carry 3L of bailout or the canister torch etc. (see below)

Switchable loop/regulator system Switchable loop/regulator system DSV/BOV
I acquired a second hand Bob-DSV. This replaces the original mouthpiece which is just on or off with a system where the off position connects you to a conventional regulator on the Diluent. To try and get around the problem of the whole thing becoming too stiff with a second hose to your mouth Bob made this swivel and, although it seems a bit strange at first, it seems to work quite well.

I decided a DSV might be a good move after a run in with CO2 breakthrough where I discovered elevated CO2 levels hit my breathing reflex so hard that I was not able to switch to the bailout as as I was taught as stopping breathing, even for the few moments needed to change to a regulator, was simply not an option. I solved the problem at the time by exhaling through my nose so the ADV fed me new gas rather than breathing the loop and recovered enough to be able to swap onto my bailout gas.

Although this will only connect me to the small onboard DIL bottle it might, if ever I find myself in that situation again, enable me to come down to the point where the stage regulator is not a step to far. I've had one go at CO2 so I hope I never need to find out for sure.

I originally though the CO2 hit was down to me loose packing the scrubber and I resolved to always bang it down hard but, after talking to Martin Parker I'm not so sure now. Whatever it was it wasn't fun and I don't want to do it again. I still pack it a bit more firmly than their demo video but not as solidly as I once did.

Torch mount Torch mount
After an unhappy couple of years with a Halcyon Proteus 6 10W HID with a determined habit of either flooding or breaking the very expensive bulb I realised that I'd never had a complete dive out of it and sold it on Ebay as "flooded - can't be bothered to mend it again!" and bought a Fa-Mi LED 75 unit and it's been quite good. Admittedly I didn't think much of their take on a Goodman Handle so I rebuilt it to suit my ideas but the torch bit just works - light when I want it. I hope it will stay that way. I mounted it on another Metalsub bracket but on the right hand side. I also have a 3L pony of air I clip on here to provide support to an OC buddy on a single or for those times when it is my turn to bag the shot up.

Vision head Vision handset Vision Electronics
The big mod for 2006 was upgrading the electronics to the new Vision system with the trimix software and the temp-stick scrubber monitor. As this is the new standard I won't bother to write it up in detail. I have run the scrubber over four hours, OK the last hour was in the pool, and I like the way it reads. I still wouldn't plan a dive to run over the usual 3 hours but if, for example my buddy had a problem that put him onto the far less efficient bailout for deco it would mean I could stay with them far more happily.

Now I did have a problem when a fault developed where the control computers in the head stopped communicating with the wrist console and the displays locked up but APD swapped the head and promised a software mod to provide warnings if it happened again. Certainly finding it back on the boat still reading 1.25bar ppO2 was a bit unsettling. See later...

Removable lungs Scooter strap Removable counter-lungs
Another rather nice trick is to make the counterlungs removable so I can leave the rig in the car and take just the lungs up to my posh hotel room and clean them out in the sink. This is so good it deserves its own page as the strip down took me places I hadn't been before.

The clips are discretely tucked down at the back and give the impression of being very secure. The new arrangement works well and on longer trips things get cleaned more often which must be a good idea. Brent, the supplier of this mod, has a web site for more details.

He also made me a very nice scooter pull-along strap. It clips onto the D ring at the bottom of the back pad and pulls crotch-strap style.

CD lift bar Custom Diver's handle
The little fabric loop handle has always been a pain when we've been trying to drag the thing back into the club RIB as it takes one hand and people keep straying towards the big, grab-able hoses. Now I have a solid stainless steel bar at the top to act as a hand magnet that they can lift it by. I wasn't quite so happy with the way the dimensions didn't match as it wasn't as simple as 'drill some extra holes and do up the bolts' which was implied. However once the sense-of-humour failure was over and larger tools were brought to bear and it all ended up together. It's another half a kilo working for me so the lead goes down.

Fourth Cell Fourth Cell
After the problem with the handset locking up I decided to add an independent readout of the ppO2 by adding a fourth cell and wiring it to my VR3 dive computer.

I selected the Narked at 90 kit and it installed pretty easily. The VR3 runs inverted (buttons at the top) on my right wrist (the Vision is on the left) and the cable comes over my right shoulder.

I am not planning on letting the VR3 use the readings for its decompression algorithm, I prefer it to use the setpoint setting controlled by three cells having seen how they vary but I do want a check readout so if things ever freeze up again I have some confirmation that the set point is still being controlled as we have been promised.

Stages Stages
Well I guess these two are to be considered 'add ons' even though they have been with me a long time. My two 7 litre 232bar stages that go decompression diving with me just in case...

They have the usual lashing kit with a piston clamp at either end, a Scubapro DIN regulator set with a contents gauge on a short hose and an APD whip to attach to the standard injector on the counterlungs.

I carry one filled with a bottom mix, normally 18/40 Trimix, and the other filled with 100% oxygen. Hung the usual 'rich on the right' way round they are on the correct side for the required counterlung injector.

I base my dive plans on these two tanks as the worst case is a total flood of my rebreather and my ascent is then on these. It's actually not very limiting as I plan it on raw Bühlmann timings with no gradient factors or other conservatism although I use a breathing rate for 'nervous' which I expect to get better as 'bored' so I can extend the deco stops.

Aside from that, which gives me a max bottom time for a depth, I do no other dive planning and set both my computers to minimum conservatism and following the most restrictive and then adding extra time from my head. The logic behind this is that I have a bad fault and have to blow through some stops I want to be able to tell the boat crew that I have missed X minutes where X is a real number and not padded by some extra safety margin. My conservatism comes from slow ascents (about 3-4 meters a minute) and extending all the required stops especially the deeper ones. I like to stay well away from the bent/not bent line deep where the gas flows are at their fastest, and any error makes a big difference, while shallow, where the gas flows are small I will not add so much. It worked out as a bit more conservative than 20/80 GF when I plotted a couple of dives. Basically the computers are a guide. I plan the deco.

I had them along on a twelve dive holiday to the Outer Hebrides in 2007 and by cross filling my on board 3L tanks from them I still went home with 90bar in each. The only fills I got from the boat were air in the suit inflate. That's diving down to over 40 meters. When I remember how I used to plough through gas when I first got the rebreather it's quite satisfying.

Tools Tools
No discussion of add-ins would be complete without the tools I added.
Now AP supply you with a tool for undoing the scrubber top hose and the vital interstage pressure gauge to check the first stages are not creeping up but there are a couple of other ones that help.

These are my favourite three.

The top one is a loop hose tool that engages the pins inside the end of the hose so you can do up and undo the ends. Several people do then now but mine came from Oxycheq in the USA.

The middle one is the T-piece C-spanner. AP do a cheap one in plastic but it is a total pain to use so you are thankful you don't need it often. This one is laser cut stainless steel so it will go on and on. It was mentioned on the excellent and is made in small batches by a man in Belgium for 25€ + 10€ shipping.

The third is the simple stainless steel Sea-Spanner. Salt water trashes adjustables too fast but this one lives in my dive box in a pool of water and if it gets stiff I splash some water on it to get off the salt encrustation and we are back in business. Web search it. It's a yottie tool from some company in NZ (notice the bottle opener in the handle). About £25.

Finally: Why did I part with it?
When I first started I wrote
"No, no way. I like the fully closed idea and will stick with it although, as you will have gathered, I'm not very impressed with some of the details on the unit I have. However I'm still happy to believe it is one of the best available. It sure beats O/C both in use and for safety.
That rather sums up the following years. I dived and made changes and dived some more. I progressed from a rather green CCR novice to somebody for who diving is CCR diving. I've never been a very skilful diver - I have to work hard to learn my in-water drills and practice to retain them but I do the time and although I had problems I fixed most of them and progressed.

In the end it was just getting older that took is toll. I'm not supple and I was finding it very hard to work stages as deep dive bailout because of the way the harness was designed. I started to look at other rebreathers and the various DIY Insperation varients to try and get a fix.

It all came to a head on a course with Zero Gravity Diving where I discussed it with Dave the instructor and he suggested trying his Sentinel. I said yes. I tried it, I liked it so I ordered one. When it came I leant the Inspo to a friend for a year to make sure I stuck to the new one until I was sure it was for me or not and another few months after it came back I sold it.

It was an old friend. We had a lot of fun together. I didn't want it to just sit in a box until it was scrap. I hope it's still out there having fun.