Hollis Explorer User Manual - page 57
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4. To warn of rare situations when excessively high CO
2
levels may require
immediate bailout to safe open circuit gas.
DANGER: The CO
2
sensor should NOT be used to determine
absorbent duration.
NOTE: As more actual dive data becomes available it may be
possible to model the CO
2
curves and generate some level
of prediction of remaining absorbent life. This is currently a
work in progress.
CO
2
– CARBON DIOXIDE SENSOR FOR EXPLORER
This section describes the operation of the CO
2
sensor as fitted to the
EXPLORER rebreather.
The EXPLORER CO
2
sensor is the world’s first commercially available car-
bon dioxide sensor proofed and designed by VR Technology for operation
in a high humidity, high oxygen rebreather breathing loops.
The CO
2
sensor actively measures carbon dioxide while the user is breath-
ing on the loop. It can thus warn of high CO
2
levels before unconscious-
ness or other symptoms occur, in time for the user to perform remedial
tasks such as finishing a dive, reducing activity or even bailing out to other
gas sources.
BACKGROUND
It should be noted that this is the first use of a CO
2
sensor in an active-user
breathing loop. As such, new data on CO
2
levels will be obtained that will
identify areas of adjustment of common practice and improved use of the
CO
2
readings as time goes on.
Much of the research in CO
2
poisoning has been conducted with military
levels of exertion and requirements. From this research the 5 to 10 mBar
limits for CO
2
were formalized as the upper working range for CO
2
by a
diver undergoing considerable exertion. Thus the alarm levels within the
EXPLORER have been initially set as 5mB and 10mB. As the user moves
into the 5 mB+ range, although no symptoms may occur, it is highly advis-
able that the dive be terminated as soon as possible.
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