Description
The RKI Instruments ES-1821 is a replacement electrochemical carbon monoxide (CO) sensor. RKI also lists it for the 03 Series and GasWatch 2. It also fits the GX-2009, GX-2012, GX-6000 and Gas Tracer, all of which RKI has discontinued; RKI still lists the part for them. On the GX-6000 the CO channel reads 0-500 ppm (1 ppm), as RKI states. Part of GX-6000 parts. Ships in 1–2 business days; most orders arrive in 3–7 business days.
RKI Instruments ES-1821 specifications
| Item | RKI Instruments data |
|---|---|
| Part number | ES-1821 |
| Type | Carbon Monoxide Sensor |
| RKI parts-list description | Sensor, Carbon Monoxide (CO) 0-500 ppm for GX-2009/GX-2012/GX-6000/CO-03/GasWatch 2/Gas Tracer |
| Gas detected | Carbon monoxide (CO) |
| Measuring range on the GX-6000 | 0-500 ppm (1 ppm) |
| RKI preset alarms on the GX-6000 | A1 25 ppm (0-500 ppm range, 1 ppm) |
| Fits | GX-2009, GX-2012, GX-6000, 03 Series, GasWatch 2, Gas Tracer |
Source: RKI Instruments GX-6000 product page https://www.rkiinstruments.com/product/gx-6000-gas-detector/, fetched Nov 8 2026; RKI Instruments 03 Series product page https://www.rkiinstruments.com/product/03-series-single-gas-detector/, fetched Nov 8 2026; RKI Instruments 2026 parts list (description).
Instruments the ES-1821 fits
| Instrument | What RKI states | On our site | Price |
|---|---|---|---|
| GX-2009 | Named in the RKI Instruments 2026 parts list. RKI: "The GX-2009 has been discontinued. Please see GX-3R gas monitor" | Not stocked; RKI has discontinued it | |
| GX-2012 | Named in the RKI Instruments 2026 parts list. RKI: "The GX-2012 has been discontinued. Please see GX-6100 as an alternative" | Not stocked; RKI has discontinued it | |
| GX-6000 | Listed in the GX-6000 parts table on the RKI product page; named in the RKI Instruments 2026 parts list. RKI: "The GX-6000 has been discontinued. Please see GX-6100 as an alternative" | Not stocked; RKI has discontinued it | |
| 03 Series | Listed in the 03 Series parts table on the RKI product page; named in the RKI Instruments 2026 parts list. | Not stocked | |
| GasWatch 2 | Named in the RKI Instruments 2026 parts list. No current product page for this model on rkiinstruments.com (Nov 8 2026). | Not stocked | |
| Gas Tracer | Named in the RKI Instruments 2026 parts list. RKI: "The Gas Tracer has been discontinued. Please see GX-6100 as an alternative" | Not stocked; RKI has discontinued it |
Source: RKI Instruments GX-6000 product page https://www.rkiinstruments.com/product/gx-6000-gas-detector/, fetched Nov 8 2026; RKI Instruments 03 Series product page https://www.rkiinstruments.com/product/03-series-single-gas-detector/, fetched Nov 8 2026; RKI Instruments 2026 parts list; RKI Instruments GX-2009 product page https://www.rkiinstruments.com/product/gx-2009-gas-detector/, fetched Nov 8 2026 (discontinued statement); RKI Instruments GX-2012 product page https://www.rkiinstruments.com/product/gx-2012-gas-detector/, fetched Nov 8 2026 (discontinued statement); RKI Instruments Gas Tracer product page https://www.rkiinstruments.com/product/gas-tracer-ppm-ch4-detector/, fetched Nov 8 2026 (discontinued statement). A model we stock links to every configuration of it; the price shown is the lowest configuration.
Carbon monoxide exposure limits
| Gas | CAS | OSHA PEL | NIOSH REL | NIOSH IDLH |
|---|---|---|---|---|
| Carbon monoxide (CO) | 630-08-0 | TWA 50 ppm (55 mg/m³) | TWA 35 ppm (40 mg/m³) C 200 ppm (229 mg/m³) | 1200 ppm |
Source: NIOSH Pocket Guide to Chemical Hazards: Carbon monoxide (OSHA PEL from 29 CFR 1910.1000 Table Z as listed there). TWA = 8-hour time-weighted average, ST = short-term (15-minute), C = ceiling, Ca = NIOSH potential occupational carcinogen. The limits are the published values, not a recommendation; the alarm presets a monitor ships with are RKI's and are in the specification table above.
RKI Instruments documents
- RKI Instruments MSHA datasheet (PDF)
- RKI Instruments quick reference card (PDF)
- RKI Instruments GX-2012 datasheet (PDF)
- RKI Instruments quick reference card (PDF)
- RKI Instruments GX-6000 datasheet (PDF)
- RKI Instruments GX-6000 operator's manual (PDF)
Source: RKI Instruments GX-2009 product page https://www.rkiinstruments.com/product/gx-2009-gas-detector/, fetched Nov 8 2026; RKI Instruments GX-2012 product page https://www.rkiinstruments.com/product/gx-2012-gas-detector/, fetched Nov 8 2026; RKI Instruments GX-6000 product page https://www.rkiinstruments.com/product/gx-6000-gas-detector/, fetched Nov 8 2026 (downloads list).
RKI Instruments ES-1821 questions
What is the RKI ES-1821 sensor? A replacement electrochemical carbon monoxide (CO) sensor. The specification table above gives the range and RKI's preset alarms on each instrument it fits.
What instruments does the ES-1821 fit? RKI lists it for the 03 Series and GasWatch 2; it also fits the GX-2009, GX-2012, GX-6000 and Gas Tracer, which RKI has discontinued. The fits table above says which RKI document names each one.
What range does the ES-1821 read? 0-500 ppm (1 ppm) on the GX-6000, as RKI states; RKI's preset alarms on the GX-6000 are A1 25 ppm (0-500 ppm range, 1 ppm).
Is the GX-6000 still supported? RKI's page says "The GX-6000 has been discontinued. Please see GX-6100 as an alternative", and the same page still carries the GX-6000 parts table that names this sensor.
Is the GX-2009 still supported? RKI's page says "The GX-2009 has been discontinued. Please see GX-3R gas monitor"; its 2026 parts list still names this part for the GX-2009.
Guides: when to replace sensors · bump test vs calibration · how to read a gas monitor alarm · CO exposure limit · every RKI replacement sensor by gas · the four sensor types and how to read a 4-gas meter.
Manufacturer item number: ES-1821.
Replacement carbon monoxide (CO) electrochemical sensor, 0-500 ppm, for the RKI GX-2009, GX-2012, GX-6000, CO-03, GasWatch 2 and Gas Tracer.
