Enclosed Spaces, Leak Detection, Bar Holing, Ambient Air And Flue Gas Testing For Co - BT CGA-411 Operation Manual

4. ENCLOSED SPACES, LEAK DETECTION, BAR HOLING, AMBIENT AIR AND
FLUE GAS TESTING FOR CO
A Test and Monitor an Enclosed Space Atmosphere
The CGA-411 and CGA-412 detectors may be used to test and to monitor an enclosed
space atmosphere.
WARNING: The detectors respond to natural gas (methane), carbon monoxide,
hydrogen sulfide, and oxygen. These detectors cannot be relied upon for
testing or monitoring other gases.
To Test an Enclosed Space Atmosphere. Connect an appropriate probe to the detector,
turn the instrument on by switching to the % Oxygen display, and allow it to warm up. Do not
use any filter other than a dust and water-block filter (the filter attached to the coiled hose). After
warm-up, insert or lower the probe into the space to be tested. Wait for at least 45 seconds to
make sure that all sensors have reached full response. If there is no alarm, check the readings on
the PPM CO and % GAS displays. If an alarm does sound, switch to the display whose symbol
appeared and verify the gas level causing the alarm condition. Do not enter an enclosed space if
an alarm for any gas is given.
To Monitor an Enclosed Space. To monitor an enclosed space for the gases detected by
the CGA-411 and CGA-412, first proceed as above to test the space atmosphere and then
continue to monitor using the % Oxygen scale. If an alarm is given, exit the space and then
verify the gas and its concentration by switching to the appropriate display. Alarm levels and
their visual symbols are:
Gas
Methane
Carbon Monoxide
Hydrogen Sulfide
Oxygen
WARNING: A detector should always be warmed-up in ambient air, never in an
enclosed space atmosphere.
Table 2. Alarms for % Oxygen Display
% Oxygen Display
Alarm Limit
0.5% (10% LEL)
35 ppm
9 ppm
Less than 19.5%
More than 23.0%
8
Display Symbol
GAS
CO
CO
LoO2
HiO2