The RKI ESR-A1DP-COHS is a dual carbon monoxide (CO) and hydrogen sulfide (H2S) combination replacement sensor. It is a single electrochemical sensor that detects both gases at once, occupying one sensor slot instead of two. It measures CO from 0–2000 ppm and H2S from 0–200 ppm, and is a genuine RKI replacement part sold at Industrial Safety Products with free shipping.

The RKI ESR-A1DP-COHS measures carbon monoxide (CO) from 0 to 2000 ppm and hydrogen sulfide (H2S) from 0 to 200 ppm. It is a dual-gas electrochemical sensor that reports both readings from a single sensor module.

The RKI ESR-A1DP-COHS combination CO/H2S sensor fits the GX-3R, GX-3R Pro, GX-Force, GasWatch 3, 04 Series, and GX-6100 series instruments. Confirm your monitor is one of these models before ordering, since it is a model-specific replacement sensor.

Yes. The RKI ESR-A1DP-COHS is a genuine RKI Instruments replacement CO/H2S combination sensor, available at Industrial Safety Products (industrialsafetyproducts.com) with free shipping. It is the correct combo sensor for GX-3R and GX-3R Pro instruments (also compatible with GX-Force, GasWatch 3, 04 Series, and GX-6100).

Yes. The ESR-A1DP-COHS is a combination sensor that detects both CO (0–2000 ppm) and H2S (0–200 ppm) in a single module, so it replaces both gas channels while using only one sensor slot. This frees space in the instrument and simplifies replacement compared with fitting two separate single-gas sensors.

Yes — like all electrochemical CO sensors, the ESR-A1DP-COHS has cross-sensitivities documented in the GX-3R Operator's Manual (Table 23, CO Detection). For example, 100 ppm hydrogen (H2) produces about a 17 ppm CO indication, and 99.2 ppm nitrogen monoxide (NO) reads about 38 ppm on the CO channel. Knowing these interferences helps you interpret readings correctly in atmospheres where those gases are present.

Only slightly. Per the GX-3R Operator's Manual interference chart (Table 24, H2S Detection), 1000 ppm of carbon monoxide produces only about a 2.6 ppm H2S indication, so the H2S channel is largely unaffected by CO. Larger cross-effects on the H2S channel come from nitrogen compounds — for example 99.2 ppm NO reads about 6 ppm, and 50.5 ppm NO2 reads about -4.6 ppm.

Yes. Carbon monoxide and hydrogen sulfide are two of the most common toxic hazards in confined spaces, and the ESR-A1DP-COHS covers both in a single sensor for RKI's GX-3R and GX-3R Pro confined-space monitors. With CO measured 0–2000 ppm and H2S 0–200 ppm, it lets a compact monitor track both toxics plus O2 and LEL when configured as a 4-gas instrument.

The main difference is integration: the ESR-A1DP-COHS combines CO and H2S detection into one electrochemical module that uses a single sensor slot, whereas two dedicated single-gas sensors each occupy their own slot. The combo approach saves space inside the instrument and means one part number to stock and replace, while still delivering the full CO 0–2000 ppm and H2S 0–200 ppm ranges.

The ESR-A1DP-COHS is an electrochemical dual-gas sensor. It uses two electrochemical cells within one housing that generate a small current proportional to the concentration of carbon monoxide and hydrogen sulfide, which the RKI instrument converts to ppm readings (CO 0–2000 ppm, H2S 0–200 ppm). Electrochemical sensing is the standard method for detecting these toxic gases at the low ppm levels relevant to worker safety.