RKI Instruments GX-3R Pro User manual

RKI Instruments, Inc.
www.rkiinstruments.com
GX-3R Pro
Condensed Operator’s Manual
(go to www.rkiinstruments.com/product/gx-3r-pro-gas-detector/ for full manual)
Part Number: 71-0524
Revision: A
Released: 1/17/23

2• GX-3R Pro Condensed Operator’s Manual
WARNING
Read and understand this instruction manual before operating
instrument. Improper use of the gas monitor could result in bodily
harm or death.
Maintenance of the gas monitor is essential for proper operation and
correct readings.
Bump test the instrument before each day’s use with a known
concentration of each target gas. A bump test can be done in User
Mode’s BUMP TEST item or by applying gas in Measuring Mode.
The instrument does not need to be calibrated unless it does not pass
the User Mode bump test or does not respond appropriately, as
defined by the user in Measuring Mode. For more information about
bump test and calibration requirements, see IEC 60079-29-2.

GX-3R Pro Condensed Operator’s Manual • 3
Table of Contents
Chapter 1: Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
About the GX-3R Pro . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
About this Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Chapter 2: Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Instrument Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Included Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Other Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Chapter 3: Measuring Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Start Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Turning On the GX-3R Pro . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Performing a Demand Zero . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Turning Off the GX-3R Pro . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Measuring Mode Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Monitoring an Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Combustible Gas Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Oxygen-Enriched Atmospheres. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
H2-Compensated CO Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Interference Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
CO2 Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Aspirator Adapter Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Alarms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Alarm Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Responding to Alarms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Data Logging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

4• GX-3R Pro Condensed Operator’s Manual
Chapter 4: Display Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Tips for Using Display Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Peak Screen (PEAK). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
STEL Screen (STEL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
TWA Screen (TWA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Combustible Sensor Target Gas Conversion (HC GAS LIST). . . . . . . . . . . . . . . . . . . . . . . . 44
User ID Screen (USER ID). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Station ID Screen (STATION ID). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Last Successful Calibration Date (CAL DATA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Last Successful Bump Test Date (BUMP DATA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Date, Time, and Temperature Screen (DATE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Alarm Points Screen (ALARM POINTS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Screen Inversion On/Off (INVERT SELECT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
LCD Color Scheme (LCD BACKGROUND) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Turning Bluetooth On/Off (BLUETOOTH). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Adjusting the Buzzer Volume (BUZZER VOLUME) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Changing Instrument Language Back to English (LANGUAGE) . . . . . . . . . . . . . . . . . . . . . 55
Chapter 5: User Mode and Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Entering User Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Tips for Using User Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Performing a Bump Test (BUMP TEST) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Performing a Calibration (GAS CAL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
Chapter 6: Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
Instrument Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
Replacing the Batteries (Alkaline Version). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
Recharging the Batteries (Li-ion Version) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
Replacing the Buzzer Cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Replacing the Sensor Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Replacing the Hydrophobic Dust Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

GX-3R Pro Condensed Operator’s Manual • 5
Replacing a Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
Replacing the Battery Board. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
Chapter 7: Storage and Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
Chapter 8: General Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
Appendix A: Maintenance Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
Entering Maintenance Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
Tips for Using Maintenance Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
Appendix B: Gas Select Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
Entering Gas Select Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
Tips for Using Gas Select Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
Appendix C: Interference Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
ESR-A13D-HCN, HCN Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
ESR-A13D-NO2, NO2Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
ESR-A13D-SO2, SO2Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
ESR-A13i-H2S, H2S Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
ESR-A13P-CO, CO Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
ESR-A1CP-COH, H2-Compensated CO Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
ESR-A1DP-COHS, CO Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
ESR-A1DP-COHS, H2S Detection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
WARNING: Understand manual before operating. Substitution of components may impair
intrinsic safety. To prevent ignition of a hazardous atmosphere, batteries must
only be changed or charged in an area known to be nonhazardous.

6• Chapter 1: Introduction GX-3R Pro Condensed Operator’s Manual
Chapter 1: Introduction
Overview
This chapter briefly describes the GX-3R Pro gas monitor. This chapter also describes the
GX-3R Pro Operator’s Manual (this document). Table 1 at the end of this chapter lists the
specifications for the GX-3R Pro.
About the GX-3R Pro
Using an advanced detection system consisting of up to four gas sensors, the GX-3R Pro personal
five-gas monitor detects the presence of combustible gas, oxygen (O2), carbon monoxide (CO),
hydrogen sulfide (H2S), and CO2or a super toxic gas simultaneously. The GX-3R Pro’s compact
size and easy-to-use design make it ideally suited for a wide range of applications, including
sewage treatment plants, utility manholes, tunnels, hazardous waste sites, power stations,
petrochemical refineries, mines, paper mills, drilling rigs, and fire fighting stations. The GX-3R
Pro offers a full range of features, including:
• Simultaneous monitoring of one to five gases
• Liquid crystal display (LCD) for complete and understandable information at a glance
• Ultrabright alarm LEDs
• Distinctive audible/vibrating alarms for dangerous gas conditions and audible alarms for
unit malfunction
• Microprocessor control for reliability, ease of use, and advanced capabilities
• Data logging functions
• Alarm trend data
• STEL, TWA, and over range alarms
• Peak readings
• Built-in time function
• Lunch break feature
• CSA “C/US” classified as intrinsically safe (see Table on page 7)
WARNING: The Model GX-3R Pro detects oxygen deficiency, elevated levels of oxygen,
combustible gases, carbon monoxide, and hydrogen sulfide, all of which can be
dangerous or life threatening. When using the GX-3R Pro, you must follow the
instructions and warnings in this manual to assure proper and safe operation of
the unit and to minimize the risk of personal injury. Be sure to maintain and
periodically calibrate the GX-3R Pro as described in this manual.

GX-3R Pro Condensed Operator’s Manual Chapter 1: Introduction • 7
Specifications
Table 1: Specifications
Combustible Gas,
Methane (CH4)
Calibration Standard*
Oxygen (O2)Hydrogen
Sulfide (H2S)
Carbon
Monoxide (CO)
Detection Range 0 - 100% LEL 0 - 25.0%
volume
0 - 100.0 ppm 0 - 500 ppm
Lower Detectable
Limit (LDL)
n/a n/a 0.5 ppm 3 ppm
Reading
Increment
1% LEL 0.1% volume 0.1 ppm 1 ppm
Warning
Setpoint
10% LEL 19.5% volume,
decreasing
5.0 ppm 25 ppm
Alarm
Setpoint
25% LEL 18.0% volume,
decreasing
30.0 ppm 50 ppm
Alarm H
Setpoint
50% LEL 23.5% volume,
increasing
100.0 ppm 1200 ppm
STEL Setpoint n/a n/a 5.0 ppm 200 ppm
TWA Setpoint n/a n/a 1.0 ppm 25 ppm
* The GX-3R Pro is also available set up for general hydrocarbons and calibrated to a combustible gas other than
methane, such as isobutane. Consult RKI Instruments, Inc. for further information.
Table 2: IR Sensor Specifications
Carbon Dioxide (CO2)
Detection Range 0 - 10.00% volume 0 - 10,000 ppm
Lower Detectable Limit
(LDL)
0.05% volume 300 ppm
Reading Increment 0.01% volume 20 ppm
Warning Setpoint 0.50% volume 5,000 ppm
Alarm Setpoint 3.00% volume 5,000 ppm
Alarm H Setpoint 3.00% volume 5,000 ppm
STEL Setpoint 3.00% volume n/a
TWA Setpoint 0.50% volume 5,000 ppm

8• Chapter 1: Introduction GX-3R Pro Condensed Operator’s Manual
Table 3: EC Sensor Specifications
Ammonia
(NH3)
Hydrogen
Cyanide (HCN)
Nitrogen
Dioxide (NO2)
Phosphine
(PH3)
Sulfur
Dioxide (SO2)
Detection Range
and Service Range
0 - 400.0 ppm 0 - 30.0 ppm 0 - 20.00 ppm 0 - 20.00 ppm 0 - 100.00 ppm
Lower Detectable
Limit (LDL)
4 ppm 1.0 ppm 0.30 ppm 0.02 ppm 0.20 ppm
Reading Increment 0.5 ppm 0.1 ppm 0.05 ppm 0.01 ppm 0.05 ppm
Warning Setpoint 25 ppm 5.0 ppm 2.00 ppm 0.30 ppm 2.00 ppm
Alarm Setpoint 35 ppm 10.0 ppm 4.00 ppm 0.60 ppm 5.00 ppm
Alarm H Setpoint 300 ppm 30.0 ppm 20.0.0 ppm 0.60 ppm 100.00 ppm
STEL Setpoint 35 ppm 10.0 ppm 1.00 ppm 1.00 ppm 5.00 ppm
TWA Setpoint 25 ppm 4.7 ppm 0.50 ppm 0.30 ppm 2.00 ppm
Table 4: GX-3R Pro Specifications
Sampling
Method
Diffusion
Response Time T90 within 30 seconds
Display Graphics LCD Display
Max. Distance
for Bluetooth
Connection
30 feet, unobstructed
Environmental
Conditions
• 3000 meter maximum altitude
• Operating pressure: 70 - 120 kPa (70 - 110 kPa for explosion proof)
• Pollution degree 2
•IP66/68
Operating
Temperature &
Humidity
Continuous environment: -20°C to 50°C/Below 90% RH
Temporary environment (up to 15 minutes): -40°C to 60°C/Below 95% RH

GX-3R Pro Condensed Operator’s Manual Chapter 1: Introduction • 9
Safety/
Regulatory
• ATEX: Certificate Number: DEKRA 17ATEX0103 X
II1G Ex da ia IIC T4 Ga/IM1 Ex da ia I Ma (with NCR-6309)
II1G Ex ia IIC T4 Ga/IM1 Ex ia I Ma (without NCR-6309)
• IECEx: Certificate Number: IECEx DEK 17.0050X
Ex da ia IIC T4 Ga/Ex da ia I Ma (with NCR-6309)
Ex ia IIC T4 Ga/Ex ia I Ma (without NCR-6309)
• CSA classified, “C/US”, as Intrinsically Safe. Class I Division 1 Groups A, B, C, D
T4.
Class I, Zones 0, A/Ex da ia IIC T4 Ga (with NCR-6309)
Class I, Zones 0, A/Ex ia IIC T4 Ga (without NCR-6309)
Alkaline version not verified with CAN/CSA 60079-29-1 & ANSI/ISA 60079-29-1
C US
186718
Power Supply
• Lithium ion battery pack (3.7 VDC, 200 mA)
OR
• Alkaline battery pack with 2 AAA batteries (3.0 VDC, 250 mA)
Continuous
Operating
Hours
@ 25 °C in
Measuring
Mode
(Non-Alarm
Operation)
Lithium Ion
Battery Pack
• Standard 4 gas + super-toxic EC: 25 hours (23 hours with
Bluetooth on)
• Super-toxic EC only: 50 hours
• Standard 4 gas + IR: 16 hours (15 hours with Bluetooth on)
• IR only: 24 hours
Alkaline
Battery Pack
• Standard 4 gas + super-toxic EC: 16 hours (14 hours with
Bluetooth on)
• Super-toxic EC only: 32 hours
• Standard 4 gas + IR: 7 hours (6 hours with Bluetooth on)
• IR only: 12 hours
Battery
Charger
Ratings
Input: 100 - 240 VAC, 47 - 63 Hz, 2.4 A
Output: 5.99 VDC, 2A max
Case High-impact Plastic, RF Shielded, Dust and Weather Proof (IP66/68)
Table 4: GX-3R Pro Specifications

10 • Chapter 1: Introduction GX-3R Pro Condensed Operator’s Manual
About this Manual
The GX-3R Pro Operator’s Manual uses the following conventions for notes, cautions, and
warnings.
NOTE: Describes additional or critical information.
CAUTION: Describes potential damage to equipment.
WARNING: Describes potential danger that can result in injury or death.
Included
Accessories
• Alligator clip
• Rubber boot
• Wrist strap
• Calibration cup
• Single-unit charger (included with Li-ion versions only)
Other
Accessories
• 12 VDC charger
• Multi-unit charger
• Belt clip
•SDM-3R
•RP-3R
• Aspirator adapter
• IrDA/USB Cable for connecting to a computer when using the Data Logger
Management Program (not needed if computer has an infrared port)
Dimensions
and Weight
Lithium Ion Battery Pack Version
Approximately 65(H) x 73(W) x 26(D) mm (2.6”H x 2.9”W x 1.0”D)
Approximately 120 g (4.2 oz.)
Alkaline Battery Pack Version
Approximately 65(H) x 73(W) x 34(D) mm (2.6”H x 2.9”W x 1.3”D)
Approximately 140 g (4.9 oz.)
Table 4: GX-3R Pro Specifications

GX-3R Pro Condensed Operator’s Manual Chapter 2: Description • 11
Chapter 2: Description
Overview
This chapter describes the GX-3R Pro instrument and its accessories.
Instrument Description
Case
The GX-3R Pro’s sturdy, high-impact plastic case is radio frequency (RF) resistant and is suitable
for use in many environmental conditions, indoors and out. The case is dust proof and water
resistant. A clear plastic window on the front of the case allows for LCD viewing. The black
bottom cover, located on the bottom of the case, allows access to the filters and sensors. A sensor
retainer and filter gasket help orient and retain the sensor and filters.
Three threaded inserts on the back of the case allow for installation of an alligator clip or belt clip.
LCD
A digital LCD (liquid crystal display) is visible through a clear plastic window in the top case.
The LCD simultaneously shows the gas reading for all installed sensors. The LCD also shows
information for each of the GX-3R Pro’s operating modes.
WARNING: A thin protective film covers the display to prevent scratches during shipping.
Remove this film before use. Leaving the film installed voids the intrinsically safe
certification.
GX-3R Pro
POWER
MODE
AIR
BackFront
LCD
Alarm
LEDs
Buzzer
Opening
Charging
Socket
Sensor
Retainer Bottom Cover
Threaded
Inserts
CO/H2SLELO2TOXIC
Figure 1: Component Location

12 • Chapter 2: Description GX-3R Pro Condensed Operator’s Manual
Control Buttons
Two control buttons, AIR and POWER MODE are located below the LCD.
Alarm LEDs
Five sets of red alarm LEDs (light emitting diodes) around the edge of the case alert you to gas,
low battery, and failure alarms.
Buzzer
One solid-state electronic buzzer is located inside the case. Sound exits the case through a hole in
the middle front of the case. The buzzer sounds for gas alarms, malfunctions, low battery voltage,
and as an indicator during use of the GX-3R Pro’s many display and adjustment options.
Vibrator
A vibrating motor inside the GX-3R Pro case vibrates for gas alarms, unit malfunctions, and as an
indicator during normal use of the various modes of the GX-3R Pro.
NOTE: If STEALTH is set to ON, the vibrator only functions when VIBRATION in the
STEALTH Gas Select Mode item is set to ON. See page 112.
Table 5: GX-3R Pro Control Button Functions
Button Function(s)
AIR • turns on LCD backlight
• resets alarm condition if LATCHING is set to ON in Maintenance Mode
• enters User Mode, Maintenance Mode, and Gas Select Mode when used
with POWER MODE button
• activates the demand zero function (adjusts the GX-3R Pro’s fresh air
reading)
• changes the value of a parameter available for adjustment
• scrolls through parameter options
POWER MODE • turns the GX-3R Pro on and off
• turns on LCD backlight
• enters and scrolls through Display Mode
• enters instructions into the GX-3R Pro’s microprocessor
• resets alarm condition if LATCHING is set to ON in Maintenance Mode
• enters User Mode, Maintenance Mode, and Gas Select Mode when used
with AIR button

GX-3R Pro Condensed Operator’s Manual Chapter 2: Description • 13
Sensors
The GX-3R Pro uses four sensors to monitor up to 5 gases simultaneously. The sensor retainer
and bottom cover hold the sensors in place. The sensors use different detection principles, as
described below.
Combustible Gas Sensor
The combustible gas sensor detects combustible gas in the % LEL range using 2 catalytic
elements: a standard element and a poison-resistant element that is resistant to sensor poisons like
silicone. The element’s resistance changes based on the reaction of gas with oxygen. The change
in resistance affects the current flowing through the element. The GX-3R Pro’s circuitry amplifies
the current, converts the current to a gas concentration, and displays the concentration on the
LCD.
The standard calibration for the combustible gas sensor is to methane but the sensor will still
detect and respond to a variety of combustible gases.
O2/CO/H2S/Super Toxic Sensors
The O2, CO, H2S, and super toxic sensors are electrochemical cells that consist of two precious
metal electrodes in a dilute acid electrolyte. A gas permeable membrane covers the sensor face
and allows gas to diffuse into the electrolyte. The gas reacts in the sensor and produces a current
proportional to the concentration of the target gas. The GX-3R Pro’s circuitry amplifies the
current, converts the current to a gas concentration, and displays the concentration on the LCD.
There are 4 different types of CO and H2S sensors available:
• CO only (ESR-A13P-CO): A single electrochemical cell that detects CO.
•H
2compensated CO (ESR-A1CP-CO-H): A single electrochemical cell that detects CO.
This sensor does not respond to or responds minimally to hydrogen (displays H2 RICH
once H2concentration reaches 2000 ppm).
•H
2S only (ESR-A13i-H2S): A single electrochemical cell that detects H2S.
•CO/H
2S (ESR-A1DR-COHS): A combination electrochemical cell that detects both CO
and H2S.
IR Sensors
The infrared sensors detect CO2in the ppm and % volume ranges. Gas enters the sensor through
an opening on its face. Infrared light shines through the gas and into an infrared detector. The
intensity of the infrared light changes with the gas concentration and this change is converted to
an electrical signal. The GX-3R Pro’s circuitry converts the signal into a gas concentration and
displays the gas concentration on the LCD.
Dummy Sensors
A dummy sensor is installed in any units that have less than 4 sensors. Dummy sensors are factory
installed. The flat side of the dummy sensor faces away from the GX-3R Pro and the hollow side
faces toward the GX-3R Pro.

14 • Chapter 2: Description GX-3R Pro Condensed Operator’s Manual
Filters
Combustible Gas Sensor H2S Removal Filter Disk (Dark Red)
An H2S removal filter disk is placed into a recess in the filter gasket over the combustible gas
sensor. The filter disk prolongs the life of the combustible gas sensor by preventing H2S in the
ambient air from reaching the sensor. The H2S filter disk is dark red in color and although it may
darken over time, its color is not indicative of remaining filter life.
The H2S filter disk needs replacing once it’s been exposed to 33 ppm hours of H2S. This means
the filter needs replacing after 80 minutes of exposure to 25 ppm H2S which equates to 40 2-
minute calibrations with a cylinder containing 25 ppm H2S. If H2S exists in the monitoring
environment, the H2S filter disk will have to be replaced more frequently.
CO/H2S Sensor Dual Filter (Black and White)
A dual filter is placed into a recess in the filter gasket over the dual CO/H2S sensor. The black half
is a charcoal filter for the CO sensor. The white half is a humidity filter for the H2S sensor.
Replace the filter if you notice:
• Unexplained CO readings.
• For users with a 1 ppm H2S alarm setpoint: A drift on the H2S zero reading, unexplained
H2S readings, the filter appears dirty, or every 6 months (whichever is sooner).
CO Sensor Charcoal Filter (Black)
A black charcoal filter is placed into a recess in the filter gasket over the CO sensor. The charcoal
filter disk scrubs H2S and certain hydrocarbons out of the sample to avoid false CO readings. If
false or elevated CO readings are noticed, especially in the presence of H2S, change the charcoal
filter.
H2S and PH3Sensors’ Humidity Filter (White)
A white humidity filter is placed into a recess in the filter gasket over the H2S or PH3sensor (if an
H2S or PH3sensor is installed). The filter absorbs humidity in the sampling environment to
prevent unstable readings around 0 ppm. “H2S” and “PH3” are printed on the side of the filter.
•H
2S: For users with a 1 ppm H2S alarm setpoint, the filter should be replaced every 6
months, if you notice a drift on the zero reading, or if the filter appears dirty (whichever is
sooner). For users with a 2 ppm or higher H2S alarm setpoint, the filter does not
necessarily ever need to be replaced.
•PH
3: The filter should be replaced every 6 months.
NO2and SO2Sensors’ H2S Removal Filter Disk (Tan)
An H2S removal filter disk is placed into a recess in the filter gasket over the NO2or SO2sensor
(if an NO2or SO2sensor is installed). The filter disk prolongs the life of the sensor by preventing
H2S in the ambient air from reaching the sensor. The filter should be replaced every 6 months.
HCN Sensor’s H2S Removal Filter Disk (Dark Gray)
An H2S removal filter disk is placed into a recess in the filter gasket over the HCN sensor (if an
HCN sensor is installed). The filter disk prolongs the life of the sensors by preventing H2S in the
ambient air from reaching the sensor. The filter should be replaced every 6 months.

GX-3R Pro Condensed Operator’s Manual Chapter 2: Description • 15
NH3Sensor’s Humidity Filter (White)
A white humidity filter is placed into a recess in the filter gasket over the NH3sensor (if an NH3
sensor is installed). The filter absorbs humidity in the sampling environment to prevent unstable
readings around 0 ppm. The filter should be replaced every 6 months. “NH3” is printed on the
side of the filter.
Hydrophobic Dust Filter
The oval-shaped hydrophobic dust filter is attached to the top of the filter gasket, covering the
sensor ports and the filters. The filter gasket and hydrophobic dust filter get replaced as a set.
NOTE: Some GX-3R Pros have a hydrophobic dust filter that is not attached to the filter gasket.
When replacing the hydrophobic dust filter on one of these GX-3R Pros, remove the
filter and the gasket and replace it with a filter gasket/hydrophobic dust filter assembly.
Infrared Communications Port
An infrared (IR) communications port is located on the top of the case, near the top LEDs.
Logged data transmits through the port in standard IrDA protocol. A computer’s infrared port or
an IrDA/USB cable connected to a USB port can be used to download data to the GX-3R Data
Logger Management Program. See the GX-3R Data Logger Management Program operator’s
manual for data logging and downloading instructions.
Battery Pack
The GX-3R Pro is either powered by a rechargeable lithium-ion (Li-ion) battery pack or an
alkaline battery pack with 2 AAA batteries (Duracell MN2400 or PC2400). Instruments with a Li-
ion battery pack have a charging socket on the back of the instrument. Instruments with an
alkaline battery pack have a cover that allows for battery replacement.
The battery icon in the upper right of the LCD shows remaining battery life. A low battery
warning activates when the GX-3R Pro detects a low battery voltage. The GX-3R Pro sounds a
dead battery alarm when battery voltage is too low for Measuring Mode.
NOTE: Use of batteries or battery chargers not specified by RKI Instruments, Inc. will
compromise the CSA classification and may void the warranty. See page 87 and page 89
for more information.
WARNING: To prevent ignition of a hazardous atmosphere, batteries must only be changed or
charged in an area known to be nonhazardous.
AVERTISSEMENT: Pour éviter l’inflammation d’une atmosphère dangereuse, les batteries
doivent uniquement être modifiés ou facturés dans une zone connue
comme non dangereuse.

16 • Chapter 2: Description GX-3R Pro Condensed Operator’s Manual
Included Accessories
Alligator Clip
An alligator clip is installed on the back of the GX-3R Pro. The alligator clip can be used to attach
the GX-3R Pro to clothing or a belt. Teeth in the alligator clip’s jaws prevent the unit from
slipping off. The alligator clip can be rotated to change the instrument’s orientation.
Rubber Boot
A black rubber boot is installed on the GX-3R Pro.
Wrist Strap
A wrist strap is included with the GX-3R Pro and can be attached to the wrist strap installation
feature on the left side of the GX-3R Pro’s case.
Single-Unit AC Charger
The charging cable is a 4 foot cable with an AC adapter on one end and a charging plug that
connects to the GX-3R Pro on the other end.
Figure 2: Alligator Clip
Alligator
Clip
Figure 3: Charging Cable
AC Adapter
Charging
Plug

GX-3R Pro Condensed Operator’s Manual Chapter 2: Description • 17
Calibration Cup
Use the calibration cup to apply gas during a bump test, calibration, or gas test. The calibration
cup has an installation orientation to observe. “Front” and “rear” imprinting on the bottom of the
cup correspond to the front and rear of the GX-3R Pro when the calibration cup is installed. In
addition, a “front” label on the front of the calibration cup should be visible when viewing the
LCD with the calibration cup installed.
Other Accessories
12 VDC Charger
The 12 VDC charger is a 4 foot cable with a vehicle plug on one end and a plug that connects to
the GX-3R’s power jack on the other end.
Multi-Unit Charger
The multi-unit charger is a 4 foot wall plug style adapter that plugs into a bar. The bar has five 2-
foot cables coming out one side. The end of each of the five cables has a plug that connects to the
GX-3R Pro’s power jack. The AC adapter is rated 100 - 240 VAC input, 5.99 VDC output.
Figure 4: Calibration Cup
FRONT

18 • Chapter 2: Description GX-3R Pro Condensed Operator’s Manual
Belt Clip
A belt clip makes it easy to hook the GX-3R Pro to a utility belt.
SDM-3R
The SDM-3R is a calibration station for the GX-3R and GX-3R Pro. The station’s buttons can be
used for operations (Standalone Mode) or a computer can be used to control the docking station
(PC Controlled Mode). See the appropriate SDM-3R manual for more information.
RP-3R
The RP-3R is a pump that draws sample to the GX-3R Pro. See the RP-3R manual for more
information.
Aspirator Adapter
The aspirator adapter is a squeeze-bulb assembly that draws sample to the GX-3R Pro.
IrDA Cable
Unless your computer has a built-in IrDA port, an IrDA cable is needed to establish
communication between the GX-3R Pro and the Datalogging Program.
Figure 5: Belt Clip
Belt Clip

GX-3R Pro Condensed Operator’s Manual Chapter 3: Operation • 19
Chapter 3: Operation
Overview
This chapter explains how to perform confined space entry monitoring or general area monitoring
in the GX-3R Pro’s Measuring Mode.
Start Up
This section explains how to start up the GX-3R Pro, get it ready for operation, and turn it off.
WARNING: A thin protective film covers the display to prevent scratches during shipping.
Remove this film before use. Leaving the film installed voids the intrinsically safe
certification.
NOTE: The screens illustrated in this section are for a 4-gas + 0 - 10.00% volume CO2unit. The
screens displayed by your GX-3R Pro may be slightly different.
Turning On the GX-3R Pro
To illustrate certain functions, the following description of the GX-3R Pro start up sequence
assumes that the following menu items are turned on: LUNCH BREAK, CAL REMINDER,
and BUMP REMINDER in User Mode, and ID DISPLAY and AUTO ZERO in Maintenance
Mode. If any of these items are turned off, then the corresponding screens will not appear.
1. Press and briefly hold down POWER MODE. Confirm that the LCD turns on, the LEDs flash,
the buzzer sounds, and the motor vibrates before continuing with operation. Release the
POWER MODE button when you hear a beep.
2. If LUNCH BREAK is set to ON (factory setting is OFF, see page 56), the Lunch Break
Screen appears. The unit counts down from 5 seconds.
a. Continue Accumulating: To continue accumulating peak and time-weighted average
(TWA) readings from the last time the GX-3R Pro was used, press and release POWER
MODE or allow the countdown to reach 0. The short-term exposure limit (STEL) reading
is reset each time the GX-3R Pro is turned on.
b. Reset Accumulation: To reset the accumulation of peak and time-weighted average
(TWA) readings, press and release AIR before the countdown reaches 0.
7:49
5 SEC
NO :AIR
LUNCH BREAK
7:49
5 SEC
YES :MODE
LUNCH BREAK

20 • Chapter 3: Operation GX-3R Pro Condensed Operator’s Manual
3. If CAL REMINDER is set to ON (factory setting) and a calibration is due, the screen that
appears next depends on how CAL EXPIRED is set in User Mode (see page 56). The three
possible screens are described below. If a calibration is not due, the instrument displays the
number of days left until a calibration is due.
CAL EXPIRED set to
CONFIRM TO USE
(factory setting)
CAL EXPIRED set to
CANNOT USE
CAL EXPIRED set to
NO EFFECT
LCD
Sound Buzzer sounds double pulsing
tone
Buzzer sounds double pulsing
tone
None
Action • Option A, Perform calibration:
Press and release POWER
MODE to perform a
calibration. The instrument
takes you straight to the AUTO
CAL CYLINDER A screen in
User Mode’s GAS CAL\AUTO
CAL item. If Password
Protection is set to On using
the SDM-3R PC program, you
must enter a password. See
page 70 for calibration
instructions.
If the calibration is successful,
the screen above will not
appear again until the unit is
due for calibration. If the
calibration is not successful,
the screen above will again
appear in the startup sequence.
• Option B, Bypass message: To
continue without performing a
calibration, press and release
AIR.
The GX-3R Pro cannot be used
until a successful calibration is
performed. Press and release
POWER MODE to perform a
calibration. The instrument takes
you straight to the AUTO CAL
CYLINDER A screen in User
Mode’s GAS CAL\AUTO CAL
item. If Password Protection is
set to On using the SDM-3R PC
program, you must enter a pass-
word. If you don’t press
POWER MODE, the instrument
automatically goes to the AUTO
CAL CYLINDER A screen after
6 seconds. If Password Protec-
tion is set to On using the SDM-
3R PC program, you must enter
a password. See page 70 for cali-
bration instructions.
If the calibration is successful,
the screen above will not appear
again until the unit is due for
calibration. If the calibration is
not successful, the screen above
will again appear in the startup
sequence.
• Option A, Perform calibration:
To perform a calibration, press
and release POWER MODE.
The instrument takes you
straight to the AUTO CAL
CYLINDER A screen in User
Mode’s GAS CAL\AUTO
CAL item. If Password
Protection is set to On using
the SDM-3R PC program, you
must enter a password.
• Option B, Bypass message: To
continue without performing a
calibration, wait a few seconds
for the instrument to continue
with its startup sequence.
7:49
CONFIRM TO USE
USER MODE:MODE
NO :AIR
CAL DATE PAST
7:49
CANNOT USE
USER MODE:MODE
CAL DATE PAST
7:49
NO EFFECT
USER MODE:MODE
CAL DATE PAST