GX-3R Pro Operator’s Manual
Chapter 6: Maintenance
•
124
NH
3
Sensor Filter
The humidity filter is white in color. The filter should be replaced every 6 months. “NH3” is
printed on the side of the filter.
Replacement Procedure
1. Verify that the GX-3R Pro is off.
2. Turn the GX-3R Pro upside down.
3. Use a small Phillips screwdriver to unscrew the two screws holding the bottom cover to the
rest of the GX-3R Pro’s case. Only unscrew them until the heads are flush with the edge of the
bottom cover.
4. Using a small flat blade screwdriver, gently pry each side of the bottom cover away from the
rest of the GX-3R Pro’s case.
5. Remove the bottom cover from the rest of the GX-3R Pro’s case.
6. Remove the filter gasket/sensor retainer assembly.
7. Remove the filter gasket/hydrophobic dust filter assembly.
8. Gently pry out the filter you want to replace.
9. Install the new filters.
a. Dark red H
2
S scrubber disk for combustible gas sensor: The brown side of the filter case
should face toward the GX-3R Pro.
b. Black and white combo filter for CO/H
2
S dual sensor: The red side of the filter case
should face toward the GX-3R Pro. The black filter material should face the edge of the
GX-3R Pro while the white filter material should face the H
2
S scrubber disk.
c. Black filter for CO-only sensor: The red side of the filter case should face toward the GX-
3R Pro.
d. White filter for H
2
S-only, NH
3
, and PH
3
sensors: The white side of the filter case should
face toward the GX-3R Pro. “H2S” and “PH3” are printed on the side of the filter
intended for use with the H
2
S-only and PH
3
sensors. “NH3” is printed on the side of the
filter intended for use with the NH
3
sensor.
e. Tan
H
2
S scrubber disk for NO
2
and SO
2
sensors: The white side of the filter case should
face toward the GX-3R Pro.
f. Dark
gray
H
2
S scrubber disk for HCN sensor: The white side of the filter case should face
toward the GX-3R Pro.