GX-3R Gas Detector

The GX-3R, weighing just 3.52 ounces and measuring 2.2" W x 2.55" H x 1.02" D, is the world's smallest 4-gas monitor. It can be conveniently clipped within a worker's breathing zone and simultaneously monitors and displays LEL combustibles, O2, CO (with hydrogen-compensated CO available), and H2S.

This device represents a cutting-edge advancement in gas detection technology, featuring a new generation of micro sensors. The LEL sensor is uniquely designed with two active filaments, enhancing its resistance to silicone poisoning; if one filament becomes poisoned, the second one takes over. The new O2 sensor is electrochemical with a 3 to 5-year lifespan, and H2S and CO are now available in a combo micro sensor.

For added safety, the GX-3R includes a non-compliance indicator that flashes its 3 LED lights every 30 seconds under specific conditions: if the instrument hasn't been bump tested, if calibration is due, or if there was a gas alarm event. The 30-second interval is adjustable, and the LEDs continue to flash until the non-compliance condition is resolved.

As low as $520.00


Compact and Lightweight: The GX-3R weighs only 3.52 ounces and has a small size (2.2” W x 2.55” H x 1.02” D), making it comfortable for workers to wear in their breathing zone. This compact design enhances mobility and comfort for the user.

Comprehensive Gas Monitoring: It simultaneously monitors and displays the levels of various gases critical for safety, including LEL combustibles, O2, CO (with hydrogen-compensated CO also available), and H2S. This comprehensive monitoring capability ensures that workers are protected against multiple potential hazards.

Advanced Sensor Technology: The GX-3R employs new-generation micro sensors, offering improved performance and longevity. For instance, the LEL sensor features two active filaments, enhancing resistance to silicone poisoning, and the O2 sensor has a long lifespan of 3 to 5 years.

Non-Compliance Indicator: The instrument is equipped with a non-compliance indicator that flashes 3 LED lights every 30 seconds under specific conditions, such as when the instrument has not been bump tested, calibration is due, or there was a gas alarm event. This feature ensures that safety supervisors can easily identify and address compliance issues, enhancing safety protocols.

Enhanced Worker Safety: By being small enough to clip within a worker's breathing zone, the GX-3R helps ensure that air samples are collected precisely where it matters most—around the worker's nose and mouth. This targeted monitoring enhances worker safety by providing real-time data on potentially harmful gas levels in their immediate environment.

Multi-Gas Monitoring in a Single Device: Unlike traditional single gas monitors, the GX-3R offers the capability to monitor four different gases simultaneously, providing a cost-effective and efficient solution for gas detection needs.

Overall, the GX-3R offers improved safety, convenience, and efficiency in gas monitoring, making it a valuable tool for workers and safety supervisors in various industries where gas exposure poses a risk.


Standard Accessories:

- Alligator clip

- Protective rubber boot

- Charger

- Calibration adapter



- Smallest & lightest 4 gas monitor — 2.2" W x 2.55" H x 1.02" D, 3.52 ounces

- Simultaneous detection of 4 gases — LEL, O2, H2S & CO — H2 Compensated CO sensor available

- Simple 2-button operation

- Non-Compliance Indicator 

- Alarms: audible, visual, & vibration

- 3 user adjustable alarm levels

- Impact resistant body with removable rubber boot

- Large LCD Auto-backlit display • 25 hours of operation (Lithium-ion battery)

- Field replaceable sensors & filters

- Water and dust resistant design, IP66/68

- Stealth mode for law enforcement 



- Personal monitoring

- Confined spaces

- Refineries/petrochemical

- Utilities

- Oil and Gas

- Water/wastewater

- Fire services

- Construction



10 seconds = 10 hours

5 minutes = 300 hours

10 minutes = 600 hours

- Instrument logs user ID, station ID, Calibration & bump test history, Alarm Events & Alarm Interval Trends


RP-3R Sample Draw Pump:

- The RP-3R are compact, battery operated, motorized sample drawing pumps which attach to either the GX-3R or the GX-3R Pro to change them from diffusion operation to sample drawing operation.



Gas: Detection Range: Alarm Set Points: Continuous Operation:
Carbon Monoxide (H2 Compensated) 0-2000 ppm


1st alarm: 25.0 ppm
2nd alarm: 50.0 ppm
3rd alarm: 1200.0 ppm
TWA alarm: 25.0 ppm
STEL alarm: 200.0 ppm
Over alarm: 2000.0 ppm


25 hours
Hydrogen Sulfide (H2S) 0-200 ppm


1st alarm: 5.0 ppm
2nd alarm: 30.0 ppm
3rd alarm: 100.0 ppm
TWA alarm: 1.0 ppm
STEL alarm: 5.0 ppm
Over alarm: 200.0 ppm


25 hours
Combustible Gases 0-100% LEL


1st alarm: 10% LEL
2nd alarm: 25% LEL
3rd alarm: 50% LEL
Over alarm: 100% LEL


25 hours
Oxygen (O2) 0-40% Vol


Low 1 alarm: 19.5%
Low 2 alarm: 18.0%
High alarm: 23.5%
Over alarm: 40.0%


25 hours



Alarm  Methods
Gas Alarm Trouble Alarm
Flashing LEDs, continuous buzzer, flashing gas value, vibration Flashing LEDs, intermittent buzzer, display of error message


Common Specifications:

Sample Method




Response Time


T90 in 30 seconds




10 sec. intervals = 1- hrs. 5 min. intervals = 300 hrs, 10min. intervals = 600 hours

Logs user ID, station ID, Calibration & Bump Test history, Alarm Events & Alarm Interval Trends


Battery Options


Li-Ion battery pack with 100-240 VAC Charger

Li-Ion battery pack with 12 VDC charger and vehicle plug

Li-Ion battery pack only (no charger)

Li-Ion battery pack with 100-240 VAC and 12 VDC chargers

Li-Ion battery pack with 100-240 VAC charger and USB charger




Digital LCD displays with 7 segment plus 14 segment plus icon


Operating Temp. & Humidity


-20°C ~ +50°C [ -4°F ~ +122°F ], 10 to 90% RH, non-condensing (continuous environment)
-40°C ~ +60°C [ -40°F ~ +140°F ], 0 to 95% RH, non-condensing (temporary environment, 15 minutes)




2.2” W x 2.55” H x 1.02” D (Approx. 58 W x 65 H x 26 D mm), 3.52 ounces (approx. 100 g) without rubber booth
2.4” W x 2.63” H x 1.06” D (Approx. 61 W x 67 H x 27 D mm), 3.70 ounces (approx. 105 g) with rubber booth


Case Material


Dust and water resistant to IP-66/68 (2m,1h) approval. Drop height 23 ft




Two buttons: POWER / MODE, AIR


Power Source


Lithium-ion battery, Approx. 25 hours after a 3 hour full charge


How to Video:



Replacement Sensors:

- Carbon Monoxide (CO) 0-2000 ppm

- Carbon Monoxide (CO) 0-2000 ppm with H2 Compensation

- Hydrogen Sulfide (H2S) 0-200 ppm

- Oxygen (O2) 0-25% Vol

- Carbon Monixide (CO) 0-200 ppm / Hydrogen Sulfide (H2S) 0-2000 ppm

- Combustables (LEL) 0-100%



Spec Sheets and Manuals:

- Data Logging Manual

- Replacement Parts

- Spec Sheet


More Information
Manufacturer RKI Intruments
Description Small handheld device great for monitoring air samples in the breathing zone.
Call For Price Yes
Gas Carbon Monoxide (CO), Hydrogen Sulfide (H2S), Methane (CH4), Oxygen (O2)
4-20 mA Output No
Field Replaceable Sensor Yes
Min, Max, Avg No
Voltage Output None
Power Requirements Lithium-ion Battery
Datalogging No
Rechargeable Yes
Field Replaceable Battery Yes
Warranty 1 Year
Audible Alarm Yes
Features The GX-3R utilizes cutting-edge microsensor technology with a dual-filament LEL sensor for enhanced silicone resistance and a long-lasting electrochemical O2 sensor.
Minimum Range Gas Dependent
Mobile Fixed
Standard Range Gas Dependent
Alarms Gas Alarm and Trouble Alarm
Maximum Range Gas Dependent
Response Time Within 30 seconds (T90)
Calibration Field Calibration
Sampling Method Fan
Range Gas Dependent
Unit Features

- Smallest & lightest 4 gas monitor

- Simple 2-button operation

- Large LCD Auto-backlit display • 25 hours of operation (Lithium-ion battery)

- Field replaceable sensors & filters

- Water and dust resistant design, IP66/68


Sensor Range

Gas Dependent

- Over 20 Different Gas Variations

Resolution Gas Dependent 
Sensor Range

Gas Dependent

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