The KISS rebreather is shipped to the user in kit form, and arrives from the manufacturer in several pieces. This is a fully closed constant flow rebreather and can be ordered with some or all of the parts to build the unit for diving. A “standard” unit has a OC/CC mouthpiece, scrubber canister, counterlungs (choice of sizes), counterlung housing, 3 separate PO2 displays (now available with backlights), LPI for oxygen addition button. This allows you to add regulators, wing, backplate, harness and cylinders of your choice.
The designer/manufacturer is Gordon Smith of Jetsam Technologies, Canada. Jetsam’s aim is to produce a rebreather that, “we believe is an optimum combination of simplicity, sophistication, and reliability in a compact easy to maintain package at a price that can be described as ‘good value for the money’.”
The manufacturer also makes it clear that the unit has not been tested by any official bodies such as DCIEM or obtained a CE mark for use in Europe. The rebreather has a stark message etched permanently into the scrubber canister. “This device is capable of killing you without warning.” This is, of course, true of any rebreather, particularly a CCR.
Students are provided with a manual which is required reading before attendance of the course, and is very comprehensive at 108 pages. Theory was covered in workshop sessions throughout the week, and were discussion based, as opposed to tradition classroom sessions. Since the divers on the course are experienced instructors themselves, basic theory of gas laws etc can be revised rather than requiring extensive teaching.
Although the course is approved by the HSE (Health and Safety Executive), it is not approved for use by any training agencies at this time. There are some provisos applied by the HSE. The course is conducted in the Red Sea to allow the instructor to wear the same equipment as the students.
The students have already assembled their units at home, and have spent a day with Steve ensuring that they work correctly and pass pre-dive checks. During the first evening, cylinders are filled along with the scrubber canister. Scrubber filling is very important to avoid bypass of the exhaled "dirty" gas.
Steve is not an early riser, much to the disappointment of his students. After breakfast the next day, the first of the many discussion sessions take place. This involves pertinent questioning to try and establish how the rebreather may fail and how to do deal with those situations. The answers are generated by stimulating thought processes in the students rather than lecturing and presentation of the problems that the group are examining. This provides the students with the knowledge they need for their first training dive, which addresses the emergency procedures and bailout options available on the unit.
- Open Circuit bailout – used for a variety of problems. The students have the standard KISS rebreather mouthpiece, which has an open circuit regulator built into it. This proves very easy for divers to manage, with a simple switch that is rotated 90 degrees to alternate between OC and CC.
- Mouthpiece recovery – used when accidentally removed from the mouth. But also, can be useful for bailout to off board gas source. Mouthpiece is first closed, and allowed to float away (it has a tendency to float upwards and behind the head). Then retrieved, cleared and re-opened.
- PO2 control – since this is effectively a manual control unit, this is a continuous skill. Monitoring and making small adjustments to the PO2 to achieve a constant PO2 of choice.
- Finding dead space – some rebreathers offer better work of breathing (WOB) than others. This often depends on the counterlung placement, since the KISS has back mounted counterlungs, it offers surprisingly little WOB. There is one position (perfectly horizontal) that causes a “dead space” and makes the exhalation more difficult. It is important to recognize this, as it can be rather disconcerting.
- Diluent flush – used primarily to lower PO2. This is surprisingly skill that requires venting gas from the loop (either through the nose or by raising the upper lip and allowing the gas to escape) and breathing in to activate the ADV (Automatic diluent valve).
- Counterlung volume control – it is essential to have the correct amount of gas volume in the breathing loop. Too much and there will be an uncomfortable feeling of over-pressurisation (hamster cheeks) and increased breathing resistance. Too little and the ADV will activate, which will dilute the gas mixture and lower the PO2.
These skills are the core skills required for survival on the unit, and are practiced on each and every dive throughout the duration of the course, along with students having the opportunity dive normally with the unit.
Following this session the rebreathers are prepared for diving, this includes the pre-dive checks and estimating weight required for diving in wetsuits.
Four stages of pre-dive checks, thoroughly check the unit prior to enter the unit. Steve warns, “The first time you skip your pre-dive checks will be your last!” The four areas broken down as follows
Low Pressure – Check the breathing loop for leaks using a positive and negative pressure checks.
High Pressure – “everything that hisses”; switch on both gases, check inflators and regulators. Then switch off the oxygen to conserve gas.
Gauges – Switch on PO2 monitors.
At this stage, the divers prepare everything that they need to go diving before moving onto the 3Gs, this is to help remember the 3 important points before beginning to breathe on the unit. Gas, Gauge and Gag! This means switch the gas on (oxygen); check the gauge (PO2 display and SPG) and put the mouthpiece in your mouth. This obviously ensures that the diver has a breathable mixture in the loop, before commencing the final stage of the pre-dive checks.
Breathe – Pre-breathe the unit immediately before entering the water. Check for CO2 breakthrough and begin the chemical reaction of the scrubber material on the surface. This should be done immediately before entering the water, to ensure that the chemical reaction does not have to be restarted before the dive commences.
You will notice, if you have experience of other CCRs, that there is no mention of calibration of the unit through the pre-dive checks. This is because the KISS needs calibrating infrequently, unlike other rebreathers that require daily calibration. This procedure is taught in a workshop before diving commences.
Vigilance and monitoring PO2 are the most important things to remember when diving any rebreather, the KISS is no different. This includes checking buddies for potential problems as well as keeping in-check with your own rebreather. Often some of the “silent killers” on the rebreather such as hypoxia and hypercapnia produce symptoms that prevent the diver identifying a problem themselves by incapacitating the diver to a point where realization of the problem is impossible. Partners while diving are the only way to turn this situation around, since the signs can be more obvious; such as erratic behavior etc. Solo diving is not a recommended practice, by many experienced rebreather divers.