Product Overview
The RKI GX-3R is a diffusion 4-gas personal monitor built for confined space and breathing-zone use. At about 3.52 oz (100 g) and 2.2" W × 2.55" H × 1.02" D, it is small enough to clip in the OSHA-defined breathing zone while displaying LEL, O2, H2S, and CO at once. An optional H2-compensated CO sensor is available when hydrogen interference is a concern.
Sensors are RKI’s micro-sensor generation: dual-filament LEL (silicone-poisoning resistance with a backup filament), electrochemical O2 (typical 3–5 year life), and a compact H2S/CO combo cell on 4-gas configs. Operation is two-button. A non-compliance indicator flashes three LEDs on an adjustable interval when bump test, calibration, or a gas-alarm event is overdue.
What’s in the box (SKU 72-RA-C)
Default storefront configuration 72-RA-C is LEL / O2 / combo H2S / CO with the Li-Ion pack and 100–240 VAC charger. Typical included items:
- GX-3R monitor with alligator clip
- Protective rubber boot
- Li-Ion battery pack and 100–240 VAC charger
- Calibration adapter (cup)
Other sensor layouts and charger options are selected with the product options above. Calibration gas, regulator, and tubing are sold separately (or via GX-3R kits).
Key features
- Simultaneous LEL / O2 / H2S / CO monitoring (H2-compensated CO available)
- Audible, visual, and vibration alarms; three user-adjustable levels plus STEL, TWA, and overscale
- About 25 hours runtime on Li-Ion after a full charge (~3 hours)
- IP66/68 dust and water resistance; impact-resistant body; rated drop height 23 ft
- Datalogging: user ID, station ID, calibration and bump history, alarm events and trends
- Field-replaceable sensors and filters
- 3-year RKI warranty (materials and workmanship)
Specifications
| Gases (4-gas) | LEL combustibles, O2, H2S, CO |
|---|---|
| LEL range | 0–100% LEL (1% LEL) |
| O2 range | 0–40% vol. (0.1% vol.) |
| H2S range | 0–200.0 ppm (0.1 ppm) |
| CO range | 0–2,000 ppm (1 ppm) |
| Sampling | Diffusion (optional RP-3R clip-on pump) |
| Alarms | Audible, LED, vibration; gas + trouble alarms |
| Battery | Li-Ion; ~25 hours continuous (non-alarm) |
| Charge time | ~3 hours to full |
| Operating temp. (continuous) | -4°F to +122°F (-20°C to +50°C), 10–90% RH non-condensing |
| Ingress / drop | IP66/68 (2 m, 1 h); 23 ft drop rating |
| Size / weight | 2.2" × 2.55" × 1.02"; 3.52 oz without boot |
| Controls | POWER/MODE and AIR |
| Approvals | ATEX, CSA (see RKI documentation for markings) |
| Warranty | 3 years |
Factory alarm setpoints are user-adjustable within RKI limits. Always confirm setpoints against your site’s written program.
Calibration (GX-3R)
For a standard 4-gas GX-3R, Ideal Calibrations recommends:
- Calibration Gas Blend 0149 — RKI 4-gas mix (50% LEL CH4, 12.0% O2, 25 ppm H2S, 50 ppm CO; balance N2)
- 0.25 LPM fixed-flow C10 regulator (correct flow for this instrument; not 0.5 LPM)
- 1/8" Tygon tubing
- GX-3R calibration cup 81-1192
Bump test before each day’s use when required by your program; perform a full calibration on the interval RKI and your site specify, and after any sensor replacement. Ideal Calibrations also provides GX-3R calibration service in Melvindale, MI.
Common applications
- Confined space entry
- Oil & gas and refining
- Utilities and wastewater
- Construction and industrial maintenance
- Fire service and emergency response
Need a different sensor layout, H2-compensated CO, the RP-3R pump, or a kit with gas and regulator already matched? Use the options above or contact Ideal Calibrations for configuration help. Replacement sensors for this platform include ESR-X13P-OXY (O2), NCR-6309 (LEL), and ESR-A1DP-COHS (H2S/CO combo).
