21 • Displaying and Setting the Alarm Points Model GX-2001 Operator’s Man-
Displaying and Setting the Alarm
Points
The Model GX-2001 allows you to display and set the alarm points of the
four target gasses. Each of the target gasses has both a low (Alarm 1) and
high (Alarm 2) alarm setting. Two gasses, CO and H
2
S, have STEL and
TWA alarm points. The alarm point for oxygen is measured as a
percentage of oxygen in the atmosphere. The alarm point for HC is
measured as a percentage of the lower explosive limit (% LEL), and CO
and H
2
S alarm points are measured in parts per million (ppm). The alarm
points and their factory settings are summarized in the table below:
In the table above, Alarm 1 and Alarm 2 for HC, CO, and H
2
S refer to a
rising concentration of these gasses. The first alarm is triggered at the
Alarm 1 concentration listed in the table. For HC that would be 10% LEL,
for CO that would be 25 ppm, and for H
2
S that would be 10 ppm. The
second alarm is triggered when the Alarm 2 concentration is reached. For
oxygen, Alarm 1 is triggered when the concentration of oxygen falls below
19.5%. When the concentration of oxygen rises above 23.5%, Alarm 2 is
activated.
Table 5: Alarm Points of the Four Target Gasses
Gas
Alarm 1
Alarm 2
STEL
TWA
O
2
19.5%
Decreasing
23.5%
None
None
HC
Combustible
s
10% LEL
50% LEL
None
None
CO
25 ppm
50 ppm
200 ppm
25 ppm
H
2
S
10 ppm
30 ppm
15 ppm
10 ppm
