BT CGA-411 Operation Manual page 10

If the alarm for a display (% GAS or PPM CO) is turned off, alarms for other detected
gases (CO and oxygen in the case of % GAS, and natural gas and oxygen in the case of PPM CO)
will still be given if these gases exceed their alarm limits. However, the alarm frequency is
reduced (once every 15 seconds) to minimize interference with readings.
Alarms for the % GAS Display. The alarm for the % GAS display may be set ON or
OFF. If ON, the alarm concentration may be up to 1.0% methane (20% LEL), but no higher.
Factory set alarm is ON with an alarm limit of 1.0% methane (20% LEL). The alarm for
carbon monoxide may be selected by the user, or, if the alarm for CO is OFF, a default value of
200 ppm is used. Alarms for oxygen are 19.5% (LoO2) and 23.0% (HiO2)
Alarms for the PPM CO Display. The alarm for the PPM CO display may be ON or
OFF. If ON, the alarm concentration may be up to 200 ppm CO. Factory set alarm is ON with
an alarm limit of 200 ppm CO. The alarm for methane is the same as for the % GAS display,
or, if the alarm for % GAS is OFF, a default value of 1.0% (20% LEL) methane is used. Alarms
for oxygen are 19.5% (LoO2) and 23.0% (HiO2).
Alarms for the % Oxygen Display. Alarms for the % Oxygen display are 0.5%
methane (10% LEL), 35 ppm for CO, and 19.5 for low oxygen and 23.0% for high oxygen.
These alarms are always ON; the alarm concentrations are fixed and independent of the
limits set for the % GAS and PPM CO displays.
Alarms for % GAS Display
ON
Methane 1% or less
CO 200 ppm or less
Oxygen 19.5% LoO2
23.0% HiO2
Alarms for TRACK GAS Scale. The alarm for gas may be set up to 1.0% methane
(20% LEL) but no higher. Factory set alarm is at 1.0% methane (20% LEL). The alarm for CO
is that selected by the user or a default value of 200 ppm. Alarms for oxygen are 19.5% (LoO2)
and 23.0% (HiO2). Alarms for CO/H
Table 1. Alarm Concentration Limits
OFF
No alarm 1% or less
200 ppm or less 200 ppm or less
19.5% LoO2 19.5% LoO2
23.0% HiO2 23.0% HiO2
S and oxygen are given once very 15 seconds.
2
7
Alarms for ppm CO Display
ON OFF
1% or less
No alarm
19.5% LoO2
23.0% HiO2
Alarms for %
Oxygen Display
Always ON
0.5% (10% LEL)
35 ppm
19.5% LoO2
23.0% HiO2