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03 Series

Single Gas Personal Monitors
Combustibles, Oxygen, Hydrogen Sulfide, Carbon Monoxide

03 Series

Individuals need personal protection in hazardous areas at all times without adding extra bulky equipment, and the 03 Series can provide that kind of protection at an affordable price. The GP-03, OX-03, CO-03, and HS-03 models are personal single gas monitors designed for protection from exposure to combustible hydrocarbons, oxygen deficiency, hydrogen sulfide, or carbon monoxide.

  • Features
  • Specifications
  • Downloads
  • Spare Parts
  • Video



  • Operates 3,000 hours on alkaline
    (GP-03 operates 35 or 30 hrs on alkaline/Ni-MH)
  • Pocket size 2.1”(W) x 2.6”(H) x 0.9”(D)
  • Light weight 2.8 ounces
  • Impact, dust, and water resistant (IP-67)
  • Replaceable rubber boot
  • Data log from 5 to 300 hours with adjustable intervals
  • Audible / visual / vibration alarms
  • Automatic backlight
  • Peak Hold, STEL & TWA
  • Low battery alarm
  • Intrinsically safe, ATEX & CSA
  • 3 Year warranty H2S & CO
  • 2 Year warranty LEL & O2
  • Hazardous Material
  • Mining
  • Tunnels
  • Refineries / Petrochemical
  • Water / Wastewater Treatment
  • Pharmaceuticals
  • Utilities
  • Chemical Plants
  • Fire Services

The O2, CO, and H2S versions can be operated continuously for at least 3,000 hours on (2) AAA size alkaline batteries. The GP-03 operates for 35 hours on alkaline and 30 hours on rechargeable Ni-MH. The 03 models have 2 preset alarms that are user adjustable. Each version is also equipped with visual, audible, and vibration alarms as standard.

03 Series

Lives are not disposable.
Why should your gas detector be?

If you or your customers are growing tired of the high failure rate and the expense of disposable instruments, then consider an alternative product that will give you many years of reliability and have a lower cost of ownership than a cheap throwaway. With a three year warranty on the HS-03 & CO-03 models (2 years on GP-03 & OX-03), your customer might be surprised to find out that they don’t need to throw these instruments away. They are free to use them for as many years as they like.

Ask your customer the following questions:

Do you find that your disposable monitors have a high failure rate?
What happens if your personnel’s disposable gas monitor fails?
Is there a cost to your company with the delays of replacing a failing disposable monitor?

Does down time and lost productivity quickly outweigh the small cost difference in a reliable renewable gas detector vs. throw away?
The -03 series gas monitor is reliable, long-lasting, and cost effective. It has a digital display, can be calibrated, and is dust and water-resistant (IP-67). The HS-03, CO-03 and OX-03 models will operate for 3,000 hours on one pair of AAA alkaline batteries. The GP-03, which is one of the only single gas personal combustible monitors available, will operate for up to 35 hours on one set of batteries. The micro-processor provides 2 alarm levels, peak hold, STEL and TWA alarms, as well as a low battery alarm.

Most importantly: The 03 Series have less than a 1% warranty claim.

Model Name CO-03 HS-03 OX-03 GP-03
Gas Detected Carbon Monoxide (CO) Hydrogen Sulfide (H2S) Oxygen (O2) Combustible gas
Detection Principle Electrochemical Galvanic cell Catalytic combustion
Detection Range
0 500 ppm
(1 ppm)
0 100 ppm
(0.5 ppm)
0 40%vol.
(0.1% vol.)
0 100% LEL
(1% LEL increments)
Alarm Set Points 1st 25 ppm
2nd 50 ppm
TWA 25 ppm
STEL 200 ppm
Over 500 ppm
1st 5.0 ppm
2nd 30.0 ppm
TWA 1.0 ppm
STEL 5.0 ppm
Over 100.0 ppm
Low 19.5% vol.
High 23.5% vol.
Over 40.0% vol.
1st 10% LEL
2nd 50% LEL
Over 100% LEL
Alarm Types
  • Gas alarms: 1st and 2nd (user adjustable), OVER alarm, STEL and TWA
  • Trouble alarms: Sensor connection, low battery circuit failure, and calibration range error
Alarm Methods
  • Gas alarm: Flashing LEDs, intermittent buzzer, flashing gas value, and vibration
  • Trouble alarm: Flashing LEDs, intermittent buzzer, and display of error message
  • STEL & TWA alarms: Flashing LEDs, intermittent buzzer, flashing gas value, and vibration
Gas Sampling Diffusion
Response Time T90 in 30 seconds T90 in 20 seconds
(Alarms within
5 seconds when exposed to 12% O2)
T90 in 30 seconds
which ever is greater
5% of reading or 5 ppm CO 5% of reading or 2 ppm H2S 0.5% O2 0.5% of reading or 2% LEL
Power Options Alkaline dry cell (2-AAA size)
Alkaline dry cell (2-AAA size)
Ni-MH battery
Continuous Operation Alkaline dry cell: more than 3,000 hours
(at 25C, no backlight)
Alkaline: 35 hrs
Ni-MH: 30 hrs
Safety Rating ATEX/IECEx approved. CSA classified, C/US, as intrinsically safe, Class I, Division 1, Groups A, B, C, D
Dimensions & Weight 2.1 W x 2.64 H x 0.94 D, (54 x 67 x 24 mm); 2.8 ounces (80 g)
Display Digital LCD, gas name & concentration, auto backlighting during alarm, operation icon, battery icon
Operating Temp. & Humidity -4F ~ 122F (-20C ~ 50C);
Humidity below 90% RH (non-condensing)
Standard Accessories
  • Rubber protective boot
  • Alligator clip
  • Data logging software
  • Alkaline batteries
Optional Accessories
  • Calibration adapter
  • Charger unit
  • Calibration kit
  • Belt clip
  • Data logging download cable
  • Wrist strap
Special Functions
  • Manual backlight for LCD (automatically lit during alarm)
  • Peak hold, STEL & TWA
Warranty 3 Year warranty 2 Year warranty


Specifications subject to change without notice. 

03 Series Parts03 series spare parts
Part # Description
ES-1821 CO sensor
ES-1827I H2S sensor
NC-6264A LEL sensor
OS-BM2 O2 sensor
07-6031 Gasket for battery lid
07-6032 Gasket between top case and bottom case
07-6033 Gasket for sensor
07-6034 Rubber sheet, Black,
10-1105-01 Cross-recessed pan head screw M2×8 SUSXM7
13-0112RK Hand strap
13-0121 Alligator clip assembly with ring
13-0122 Belt clip
13-0204RK Spring pin for clip
13-1116 Screw for battery lid
15-0500 Battery contact short
15-0501 Battery contact piece (-)
15-0502 Battery contact piece (+)
20-0325 Rubber protection cover, Black
21-1908 Battery lid
21-1909 Battery contact piece holder
21-1910 Bottom case (GP-03/OX-03)
21-1911 Bottom case (CO-03/HS-03)
21-1912 Top case
21-1913 Top case asssembly
29-0652 Panel sheet RKI version (GP-03)
29-0653 Panel sheet RKI version (OX-03)
29-0654 Panel sheet RKI version (CO-03)
29-0655 Panel sheet RKI version (HS-03)
29-6100 Water immersion sensing seal
30-1055 Vibration motor
33-0175 Hydrophobic filter for sensor
33-7106RK H2S scrubber filter for CO sensor, strip of 5
49-1110RK Alkaline battery AAA (2 required)
49-1312 Ni-MH battery AAA (2 required)
51-1130 LCD module
57-1282 Main PCB assembly (GP-03)
57-1283 Main PCB assembly (OX-03)
57-1284 Main PCB assembly (CO-03)
57-1285 Main PCB assembly (HS-03)
81-1146 Calibration adapter


Specifications subject to change without notice. 

Introduction | Description | Start Up | Operation | User Setup
Calibration | Maintenance

03 Series Video


A new window will open to play the training video. Video can also be viewed on Youtube




Calibration Station for 03 Series

Calibration Station for 03 Series A single module calibration station for the 03 Series with advanced features for charging, calibration, bump testing, and archiving data.
Multi module system and can be connected to a PC for automated calibration, bump test, data archiving.

Stand Alone Calibration Station

Cal Kits

Calibration Kits for Portable and Fixed

Multi-Port Power Adapter
RKI is pleased to offer our Calibration Kit Datasheet to help our customers select the correct calibration equipment for their needs. Cal Kit PDF