18 • Instrument Description
Gas Tracer Operator’s Manual, CSA Version
Pump
A diaphragm pump inside the Gas Tracer draws the sample to the sensors. It can
draw sample from as far as 50 feet from the Gas Tracer. The pump is not user
serviceable.
CAUTION:
Sample hose lengths of more than 50 feet are not recommended for the Gas
Tracer because of flow rate reduction.
Flow Chamber
The flow chamber is on the back of the Gas Tracer and is held in place by three
phillips screws. The flow chamber seals to the rubber sensor gasket which seals to
the sensor faces inside the Gas Tracer and routes flow from the pump to the
sensors to the exhaust port (also a part of the flow chamber).
Sensors and Filters
The sensors are located underneath the flow chamber and are only accessible if
you remove the flow chamber and the sensor gasket.
An H
2
S removal filter disk is placed into a recess in the sensor gasket over the
%LEL sensor. It prevents H
2
S in the ambient air from reaching the unit’s
combustible gas sensor. Removing H
2
S that is present in the monitored air
prolongs the life of the sensor. The H
2
S filter disk is dark red in color and
although it may darken over time, its color is not indicative of remaining filter
life. The H
2
S filter disk can absorb H
2
S for 33 ppm hours and should be replaced
after that much exposure. With this many ppm hours of absorption, the H
2
S filter
disk should be replaced after 80 minutes of exposure to 25 ppm H
2
S. This equates
to replacing the H
2
S filter disk after 40 2-minute calibrations with a cylinder
containing 25 ppm H
2
S. If H
2
S exists in the monitoring environment, the H
2
S
filter disk will have to be replaced more frequently.
A charcoal filter is placed into a recess in the sensor gasket over the CO sensor.
The charcoal filter is black, has a woven texture, and is impregnated with an H
2
S
absorbing material. The CO sensor will respond if exposed to H
2
S and certain
hydrocarbon gases. The charcoal filter disk scrubs these gases out of the sample to
avoid false CO readings. If false or elevated CO readings are noticed, especially in
the presence of H
2
S, change the charcoal filter.
NOTE:
If you have a Gas Tracer that is intended for CO with H
2
S response
operation, a charcoal filter will not be installed. Do not install a charcoal
filter.
Inlet Filter Holder
The filter holder is a clear plastic dome shaped piece on the top of the case. A male
quick connect fitting is located on the inlet filter holder. This is the Gas Tracer’s
inlet fitting. A cotton dust filter is inside the filter holder. The filter holder may be
removed by turning it counterclockwise and pulling it away from the case. Two
flat membrane disk hydrophobic filters, a wire mesh disk, and a rubber filter
retaining gasket are held in place by the filter holder and are located in the bottom
of the case chamber where the filter holder is installed.
