Hollis Explorer User Manual - page 59
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respiration can occur to some degree even up to 20mB CO
2
. However, the
amount of exertion and other pressure related effects mean that this is un-
advisable, and CO
2
poisoning and death may occur at levels in the 10-20
mB range in some cases. So some of the extended durations currently ex-
perienced are due to the user taking the CO
2
level into the 5-10 mB range,
without any obvious symptoms of CO
2
poisoning.
The user must be aware that strenuous exertion when CO
2
is at these
elevated levels can quickly cause the CO
2
levels to rise rapidly. As the
symptoms of CO
2
poisoning are almost impossible for the user to recog-
nize – they will just pass out and may drown. However, the readings from
the CO
2
sensor showing that CO
2
levels are rising (while still not exhibiting
symptoms) should be used as much as anything to limit the strenuous
activity and further use of the filter after the dive has finished.
DANGER: New dives must not be performed on the filter once
CO
2
levels in the 5-10 mB region have occurred, regardless of
how short a duration. Some rebreather fatalities are possibly
due to users pushing the CO
2
filter with strenuous activity near
the end of the filter life.
Increased depth or reductions in temperature when the CO
2
filter is near
the end of its life are also not advised, as the filter is less able to cope with
high CO
2
levels. So increased depth, coupled with muscular activity and
cold are a very bad combination when near the end of filter life where CO
2
levels are already raised.
NOTE: Conversely, reducing your depth and work rate and
returning to warmer water, are all good ways to manage CO
2
levels until you can return to the surface and change the
filter. In any event if a CO
2
alarm is seen the EXPLORER will
force an immediate action to return you to the surface.
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