04 Series
Single Gas Monitors
The 04 Series by RKI Instruments is a family of pocket-sized single gas monitors designed to operate for many years with field-replaceable sensors and batteries. Available in H2S, CO, CO with H2 elimination, O2, dual CO and O2, and a range of toxic gas configurations covering NH3, Cl2, HCN, NO2, PH3 and SO2, the 04 Series provides genuine long-term personal gas protection in the same compact, lightweight housing across all variants. With up to 9,000 hours of continuous operation on two AAA alkaline batteries, three user-adjustable alarm set points, STEL and TWA monitoring, data logging and IP67 ingress protection, the 04 Series delivers more capability than any other single gas monitor in its size class.
KEY BENEFITS
- Up to 9,000 hours continuous operation on 2x AAA alkaline batteries depending on model
- Three user-adjustable alarm set points plus OVER alarm, STEL and TWA
- Pocket-sized at 54 x 67 x 24 mm and just 80 grams
- Available in H2S, CO, CO with H2 elimination, O2, dual CO and O2, NH3, Cl2, HCN, NO2, PH3 and SO2 configurations
- Field-replaceable sensors interchangeable with RKI GX-3R, GX-3R Pro and GasWatch 3
+ more in the Description tab below
Long Runtime. Small Size. Wide Range of Gases.
The 04 Series was designed to be the last single gas monitor a worker ever needs to think about. Field-replaceable sensors, long battery life and a 3-year warranty on both the instrument and sensors mean the 04 Series is built for years of reliable service without the replacement cycles that drive up fleet costs.
All 04 Series models share the same compact housing at 54 x 67 x 24 mm and 80 grams, small enough to clip to a shirt pocket and light enough to forget it is there. Despite the compact form factor, the 04 Series includes three user-adjustable alarm set points, STEL and TWA monitoring, Peak Hold, data logging and full audible, visual and vibration alarm capability as standard.
Exceptional Battery Runtime
The H2S and CO models operate for up to 9,000 hours on just two standard AAA alkaline batteries — approximately 375 continuous days. The CO with H2 elimination model operates for 6,200 hours, the O2 model for 3,000 hours, the dual CO and O2 model for 4,600 hours and the toxic SC-04 models for 3,000 hours. No recharging, no power management, no scheduled battery replacements in the middle of a shift.
Interchangeable Sensors Across the RKI Fleet
04 Series sensors are field-replaceable without tools and are interchangeable with sensors used in RKI’s GX-3R, GX-3R Pro and GasWatch 3 instruments. This simplifies spare parts management for organisations running mixed RKI fleets and means technicians only need to stock one sensor type across multiple instrument platforms. Sensors have a life expectancy of over 3 years and are backed by a 3-year warranty, with the exception of NH3 and Cl2 sensors which carry a 1-year warranty.
Data Logging and Compliance
Every 04 Series model logs gas readings, alarm events, alarm trends, calibration and bump test history and instrument settings. The logging interval is adjustable from 10 seconds to 10 minutes, providing between 10 and 600 hours of data storage. Data is downloaded to a PC via IrDA using the included data logging software for compliance reporting and incident investigation.
Built for Hazardous Locations
All 04 Series models carry IP67 ingress protection and are certified as intrinsically safe under ATEX and IECEx, and by QPS to US and Canadian standards for Class I, Division 1, Groups A, B, C and D atmospheres.
Benefits
- Up to 9,000 hours continuous operation on 2x AAA alkaline batteries depending on model
- Three user-adjustable alarm set points plus OVER alarm, STEL and TWA
- Pocket-sized at 54 x 67 x 24 mm and just 80 grams
- Available in H2S, CO, CO with H2 elimination, O2, dual CO and O2, NH3, Cl2, HCN, NO2, PH3 and SO2 configurations
- Field-replaceable sensors interchangeable with RKI GX-3R, GX-3R Pro and GasWatch 3
- Sensors backed by a 3-year warranty (1 year for NH3 and Cl2)
- Audible, visual and vibration alarms as standard
- Peak Hold, STEL and TWA monitoring included
- Data logging from 10 hours to 600 hours with adjustable intervals
- IP67 rated for dust and water resistance
Dimensions
54 x 67 x 24 mm
Weight
80 g
Detection principle
Electrochemical
Response time
T90 in 30 seconds
Alarm set points
3 preset alarms, all user-adjustable, plus OVER alarm, STEL and TWA
Alarm types
Gas alarm: 1st, 2nd, 3rd, OVER, STEL and TWA. Trouble alarm: sensor connection, low battery, circuit failure, calibration range error
Alarm methods
Flashing LEDs, intermittent buzzer, flashing gas value, vibration
Sampling
Diffusion
Battery
2x AAA alkaline dry cell
Display
Digital LCD, gas name and concentration, auto backlight during alarm, battery icon, operation icon
Data logging
10-second intervals: 10 hours. 5-minute intervals: 300 hours. 10-minute intervals: 600 hours
Peak Hold
Yes
STEL and TWA
Yes
Operating temperature
-20°C to 50°C
Humidity
0 to 90% RH non-condensing
IP rating
IP67
Safety rating
ATEX and IECEx intrinsically safe. QPS classified C/US, Class I, Division 1, Groups A, B, C and D
Sensor life
Over 3 years
Warranty
3 years including sensors (1 year for NH3 and Cl2 sensors)
Chlorine
Cl2
Carbon Monoxide
CO
Hydrogen Sulphide
H2S
Hydrogen Cyanide
HCN
Ammonia
NH3
Nitrogen Dioxide
NO2
Oxygen
O2
Phosphine
PH3
Sulphur Dioxide
SO2
- Aviation & Transportation
- Chemical Manufacturing
- Confined Space & Compliance
- Energy (Oil & Gas)
- Food & Beverage
- Landfill & Remediation
- Marine & Maritime
- Medical & Healthcare
- Mining & Minerals
- Power Generation & BESS
- Technology & Semiconductor
- Water & Wastewater
The 04 Series includes the HS-04 (H2S), CO-04 (CO), CO-04C (CO with H2 elimination), OX-04 (O2), CX-04 (dual CO and O2) and SC-04 (toxic gases including NH3, Cl2, HCN, NO2, PH3 and SO2). Contact Gastech to confirm the right model for your application.
Battery runtime depends on the model. H2S and CO models operate for up to 9,000 hours on two standard AAA alkaline batteries. Other models range from 3,000 to 6,200 hours depending on the gas type.
Yes. 04 Series sensors are interchangeable with sensors used in the RKI GX-3R, GX-3R Pro and GasWatch 3, simplifying spare parts management across a mixed RKI fleet.
The 04 Series carries a 3-year warranty on material, workmanship and sensors for most gas types. NH3 and Cl2 sensors carry a 1-year warranty.
Yes. All 04 Series models are certified as intrinsically safe under ATEX and IECEx, and by QPS to US and Canadian standards for Class I, Division 1, Groups A, B, C and D atmospheres.
Yes. All 04 Series models log gas readings, alarm events, calibration and bump test history and instrument settings. Logging intervals are adjustable from 10 seconds to 10 minutes providing between 10 and 600 hours of data storage.
The CO-04C uses a hydrogen-resistant CO sensor, reducing cross-sensitivity to hydrogen gas. This is useful in environments where H2 may be present alongside CO, such as battery rooms or hydrogen fuel cell applications, where a standard CO sensor could produce false alarms.
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