How it all started
Last summer we dived the Moldavia out of Littlehampton. Alex Towns was on the boat and had brought along his new rebreather, a KISS. I'd heard about them before, having read Steve Millard's article in 9>90 (Vol2 issue 4), but never seen one in the flesh. I've seen plenty of Inspirations, but never been that keen on them for reasons I cannot easily explain.
The KISS unit that Alex dived looked impressively simple yet beautifully engineered. Alex's had 5L tanks for diluent and O2, and these fitted the unit very nicely. In the weeks that followed, Zak (who was also on the boat) and I decided to go for it and order one each. Delivery was about 6 weeks and unfortunately meant that we did not receive the units until early September. Due to a change of job I didn't really get the chance to do any diving in the autumn apart from a couple of visits to the pool, but there was plenty of time to get it checked out and adapted how I wanted it.
About the unit
The KISS is
made in Vancouver, Canada by Gordon Smith. It's not CE approved so it
is sold as a 'kit'. In practise that means it is supplied with a few of
the O rings not yet fitted. You need to strip and rebuild the rebreather
before using it, which means you get to know exactly what goes where and
how it works. You will also find a few O rings left over afterwards, I
assume Gordon does this to make you worried that you've built it correctly
- in which case it has the desired effect!
The unit comes with an aluminium case, however Dave at Portland Engineering has designed and made a stainless steel case for the unit for several UK KISS users. The s/s case weighs in at about 7.5Kg compared to 2Kg for the aluminium one, which means no weight belt. It is also a lot more rigid, especially for the larger tanks (the original was designed for 2L tanks). Onto this a conventional backplate/wing or soft wing/harness can be bolted.
Diving the KISS
Well people say that you are back to novice level when you start diving a rebreather and it's true. The first time in the pool my bouyancy was hopeless. The problem is that controlling lung volume - which an experienced O/C scuba diver uses to good effect to control their bouyancy - does nothing. Changes in the loop volume and gas in your BC/suit are the only things that affect bouyancy. The KISS has a relatively small counterlung volume - the unit as shipped has 1 2L and 1 4L counterlung, i.e. 6L total. This is about the same as an average person's maximum lung volume. So changing the loop volume is not really possible (and not really desirable either, as you're wasting valuable gas when you vent the loop).
Out in open
water things got noticeably better at depth and with experience. The quietness
was astonishing. You could hear O/C divers a way away. Also breathing
was 'different' - with O/C one tends to breathe in, hold, breathe out.
You're concious that breathing too fast wastes gas. But with a rebreather
it makes no difference, so you breathe just like you do on the surface.
The KISS has back mounted counterlungs (inside the case for protection). This means that (in normal attitude in the water) breathing out is easy and breathing in has slightly higher resistance. The Inspiration has over-the shoulder counterlungs which tend to even out the breathing resistance at the expense of cluttering up the chest area. There are advantages and disadvantages of both, personally I like the uncluttered approach.
So the bouyancy's different, what else? Well unlike an Inspiration you have to control your ppO2 at all times. Not as bad as it sounds, since even with an Inpiration you have to know your ppO2 at all times.And the design of the KISS means that O2 is injected at a set rate (user adjustable) which approximates your bodies' consumption of O2 at rest. Why at rest? Well you don't want the loop ppO2 going up on deco stops etc, it is preferable to have it about right at rest then add O if you are working/finning hard. In practise the ppO2 does not change rapidly, if you set it to say 1.3 bar then it takes quite a while to decrease. How soon depends on your metabolism though.
Last updated: Mar 04, 2003