"
CAUTION
In either mode, correct the condition causing the excessive gas level
and vent or purge the area before attempting the following.
In the LOC % LEL mode, the output signal is also locked
at full-scale. If this condition occurs, the Toxgard II
Monitor must be unlocked by performing a "Zero
Function," either with the Ultima Calibrator or
Controller or by using the internal "CAL"
push-button.
NOTE: The Ultima Calibrator and Controller are compatible
with both the Ultima Gas Monitor and the Toxgard II
monitor.
In the LOC mode, The Toxgard II Monitor will not
revert to a normal condition until a successful zero
operation has been performed. This is an exclusive
safety feature of the Toxgard II Monitor which
pre-empts the possibility of ambiguous readings
when the sensor is exposed to concentration of gas
above 100% LEL.
In the 100% LEL mode, the combustible gas is over the
100% LEL range. It will return to normal operation
when the gas concentration level falls below 100%
LEL.
Calibration
As with any type of gas monitor, the only true check of its
performance is to apply gas directly to the sensor. The frequency
of the calibration gas tests depends on the operating time and
chemical exposures of the sensors. New sensors should be
calibrated more often until the calibration records prove sensor
stability. The calibration frequency can then be reduced to the
schedule set by the safety officer or plant manager. Before
calibrating the sensors, it is good practice to apply power to the
unit to allow the sensor to adapt to the new environment. This is
especially important for the following units:
• chlorine
• nitric oxide
• hydrogen cyanide
• hydrogen chloride
• chlorine dioxide.
Chapter 2, Start-up
2-3
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