Four Gas Monitor, confined space detector features simultaneous detection of LEL, O2, H2S & CO. World's smallest and lightest portable multigas Detector. RKI's high quality safety instrument.


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Confined Space 4 Gas Monitor


  • Smallest & lightest 4 gas monitor
  • Simultaneous detection of 4 gases; LEL, O2, H2S & CO
  • H2 Compensated CO sensor available
  • Simple 2-button operation
  • Alarms: audible, visual, & vibration
  • 3 user adjustable alarm levels
  • 25 hours of operation (Lithium-ion battery)
  • Water and dust resistant design, IP66/68
  • 3 Year warranty
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The GX-3R is the worlds smallest 4 gas monitor weighing only 3.52 ounces and can comfortably be clipped within a worker’s breathing zone (2.2” W x 2.55” H x 1.02” D). It simultaneously monitors and displays LEL combustibles, O2, CO (Hydrogen compensated CO also available), and H2S.

The GX-3R represents the latest evolution of gas detection technology utilizing a new generation of micro sensors. The LEL sensor has a unique design with two active filaments in one sensor to increase it’s resistance to silicone poisoning. If one filament gets poisoned the second filament takes over. The new O2 sensor is electrochemical with a 3 to 5 year life span.  H2S and CO are now available in a combo micro sensor.  

Safety supervisors will appreciate the non-compliance indicator. The instrument flashes it’s 3 LED lights every 30 seconds in the following conditions; if the instrument has not been bump tested, or if calibration is due, or if there was a gas alarm event. The 3 LED lights will continue to flash once every 30 seconds until the non-compliance condition has been resolved. The 30 second interval is adjustable.

OSHA defines the breathing zone as a ten inch radius around the worker’s nose and mouth, and requires that worker exposure monitoring air samples be collected in the breathing zone. Air sampling filters may be attached to the collar or lapel.  Traditionally this means only a single gas monitor would be small enough for a worker to practically wear a gas monitor ‘In the breathing zone’. Now there is a 4 gas monitor smaller than many single gas monitors.

GX-3R callouts


  • Personal monitoring
  • Confined spaces
  • Refineries/petrochemical
  • Utilities
  • Oil and Gas
  • Water/Wastewater
  • Fire Services
  • Construction


Gas Detected

H2 Compensated

Carbon Monoxide(CO) Hydrogen Sulfide(H2S) H2S

Combustible Gases
(Methane as standard)


Dual Sensor

Sensor Slot





Catalytic combustion

Detection Range

0 ~ 2,000 ppm
(1 ppm)

0 ~ 200.0 ppm
(0.1 ppm)

0 ~ 100% LEL
(1% LEL)

0 ~ 40% Vol. (0.1%)

± 5% of reading
or ± 2 ppm CO

± 5% of reading
or ± 5 ppm CO
(whichever is greater)
± 5% of reading
or ± 2 ppm H2S
(whichever is greater)

± 5% of reading
or ± 2% LEL
(whichever is greater)

± 0.5% of reading O2
Sampling Method

Diffusion sampling standard (hand aspirator or clip-on motorized pump optional)


Digital LCD displays with 7 segment plus 14 segment plus icon

Preset Alarms
(User Adjustable)
Overscale alarm
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
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
1st alarm: 10% LEL
2nd alarm: 25% LEL
3rd alarm: 50% LEL
Over alarm: 100% LEL
Types of Alarms Gas Alarm: 3 Increasing alarms, STEL, TWA, overscale alarm. O2 decreasing/increasing.
Trouble alarm: Sensor disconnection, low battery, circuit error, calibration range error
Display of Alarm Gas Alarm: Flashing LEDs, continuous buzzer (100 db @ 30 cm), flashing gas value, vibration
Trouble alarm: Flashing LEDs, intermittent buzzer (95 db @ 30 cm), display of error message
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)
Response Time Within 30 seconds (T90)
Power Source Lithium-ion battery, Approx. 25 hours after a 3 hour full charge
Approvals  ATEX,  CSA, IECEx, MED
& Weight
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
Controls Two buttons: POWER / MODE, AIR
Datalogging Logs user ID, station ID, Calibration & Bump Test history, Alarm Events & Alarm Interval Trends
Alligator clip, protective rubber boot, charger, and calibration adapter
SDM-3R calibration station
RP-3R Clip-on sampling pump with 4” rubber nipple, 10’ hose and probe (up to 40’ hose available)
Padded carrying case for GX-3R and accessories
USB to IrDA downloading cable for datalogger
Warranty Three years material and workmanship


GX-3R Spare Parts

Part # Description
07-6057 Sensor gasket, GX-3R
07-6058 Sensor case o-ring, GX-3R
10-1086 Screw with flat and lock washers, M2 x 4 phillips
10-1087 Screw, GX-3R sensor cap & battery pack, 3/16 phillips
13-0112RK Wrist strap
13-0124 Alligator clip with installation screws
13-0125 Belt clip with installation screws
20-0332 Rubber boot for GX-3R
21-1950 LCD protective film for GX-3R/GX-3R Pro
21-1962 Bottom cover (sensor cap), GX-3R
21-1963 Sensor retainer, GX-3R
21-1967 Rear case assembly with Li-ion battery, GX-3R
21-1968 Front case with overlay, GX-3R
29-0715 Label, case sensor, CO, LEL, O2, GX-3R
33-0183 Sensor dust filter with internal gasket for GX-3R
33-0183-10 Sensor dust filters with internal gasket for GX-3R, 10-pack
33-0553 Buzzer protection cover for GX-3R
33-7130 Scrubber disk filter for H2S/CO sensor 5-pack
33-7131 Scrubber disk filter for LEL sensor, 5-pack
33-7132 Scrubber disk filter, charcoal, for CO & H2 comp CO sensor, GX-3R/GX-3R Pro, 5-pack
33-7133 Humidity filter disk for H2S sensor, GX-3R/GX-3R Pro, 5-pack
51-1142 LCD module with cable, for GX-3R
57-2098 Li-Ion battery with battery board
ESR-A1DP-COHS Sensor, H2S/CO combo for GX-3R/GX-3R Pro
NCR-6309 Sensor, LEL for GX-3R/GX-3R Pro
ESR-X13P-OXY Sensor, O2 for GX-3R/GX-3R Pro
ESR-A13I-H2S Sensor, H2S for GX-3R/GX-3R Pro
ESR-A13P-CO Sensor, CO, GX-3R/3R Pro
ESR-A1CP-CO-H Sensor, CO with H2 compensation for GX-3R/GX-3R Pro
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