Manual rEvo III
26
4.4: Entering the water, bubble-check, during diving, exiting the water:
* "ALWAYS DIVE IN GREEN" When entering the water, during diving and leaving the
water, both HUD's must ALWAYS show the green LED burning, if not, correct
immediately!
* Perform a bubble-check at 3/5 meters: is the rebreather well attached? No
components hanging loose? No bubbles?
* During diving, check the readings on the displays regularly: do they correspond with
the indication on the HUD's?
*
"ALWAYS KNOW YOUR PPO2".
* Pay attention to correct positioning in the water: the lowest breathing resistance
can be achieved when diving under a slight positive angle: you can easily find the best
inclination when the breathing resistance during inhaling and exhaling is
approximately equal.
* Be careful to pay special attention to diving with a ‘minimum loop volume’:
inexperienced rebreather divers have the habit of overfilling the counterlungs: this has
a negative effect on breathing comfort; because at that moment, at the end of the
exhale, you are blowing against an almost full lung. Also a lung which is too full
provokes noticable differences in buoyancy. The correct lung volume is reached when
during a complete inhalation, the ADV is just not activated. This can be tested by
blowing off small quantities of gas through the sides of your mouth or your nose until
the correct volume has been reached. Especially during ascent, when the gases in the
loop expand, it is important to keep the lung volume to a minimum, so that a correct
PPO2 can be maintained by injecting only small bursts of oxygen.
* Make sure you always breathe regularly and deeply: this improves the good
absorption of CO2 in the scrubber (as more gas goes through the scrubber). Keeping
your breath (breath-holding) must be avoided at all times: you can not save any gas
anyway!
* When the PPO2 drops below the desired value, inject oxygen in short bursts, while
constantly breathing the loop: this prevents spikes of high PPO2 in the system.
* Always keep a very close eye on the PPO2 during ascent: due to the decrease of
pressure the PPO2 will fall: because of this it is necessary to add oxygen more often
compared to diving at constant depth. Avoid fast or uncontrolled ascents. Depending
on the depth at which you have been diving, it can be necessary to add oxygen more
often, while venting the excess gas.
Note: "Cell-Check"
See also “ How to use and when to replace oxygen cells”.
It is very important to check the correct functioning of the oxygen cells at regular
intervals: cells have the dangerous property of becoming unstable when they get
older or more used and are thus unable to indicate high PPO2 values any longer (so-
called ' current-limiting '). This means that for example a cell can correctly indicate a
PPO2 of 1.3, but when PPO2 increases, the output of the cell will not increase any
more. This is of course very dangerous because in case of current-limiting high PPO2
levels are no longer indicated!
To verify the cells the following test can be carried out: (do this together with your
buddy so he can keep an eye on you): at a depth of 6 metres, push the manual
oxygen addition button: (pay attention that your buoyancy does not increase, if
needed let gas escape through the sides of your mouth or nose). Check if the readings
on the displays of the rEvodreams indicate at least up to 1.55: the red LED of the HUD
will start blinking and the green LED must go out: this indicates a correct functioning
of the cells as they can still display a PPO2 higher then the one you will use during
diving. Next add diluent manually to bring the PPO2 to a safe level.
