15
activated. If the NO
2
alarm level is set above 9ppm, then the
external alarm comes into operation at the set level for NO
2
. The
external alarm consists of a pair of normally closed contacts, which
are latched open when the above condition occurs. This can be used
to sound an external alarm or switch a NO delivery system into safe
operating mode in systems equipped with this facility.
The display will change to:
.
15
5p
p
4m
CUTOUT:PRESSENTER
987
148
NO
NO
2
.
Measurements will continue but it should be noted that the
measurement range would be limited to just over 100ppm NO and
20ppm NO
2
and that the actual concentrations could be significantly
higher.
Press enter to clear the external alarm when the reading drops
below the external alarm levels.
When this condition occurs, the cause should be immediately
investigated. However, caution should be observed when shutting
down the supply of NO, as the sudden cessation of NO can be more
detrimental to the patient than a temporary overdose of NO.
Ideally, the external alarm should be used to switch the delivery
system into a ‘safe’ operating mode or switch in a backup supply.
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