Hydrogen Sulfide Sensors
Select H₂S sensors for personal safety, fixed industrial detection, wastewater, biogas, odor monitoring and OEM instruments. Compare electrochemical cells, digital modules, low-level 4-electrode sensors and high-range process options.
Choose the H₂S range around the exposure scenario
A worker-safety monitor and a raw-biogas analyzer can both measure hydrogen sulfide, but they are different instruments. Use the expected concentration and the measurement purpose to set the first shortlist.
0–100 ppm class
Portable detectors need fast response, compact packaging and predictable recovery after a gas pulse.
- Miniature 3-electrode electrochemical
- Check T90 and overload limit
0–100 / 200 ppm
Fixed instruments can use larger cells with more electrolyte volume and stronger long-term environmental stability.
- 20 mm / 32 mm industrial packages
- Check calibration access and enclosure diffusion
Low ppm to ppb-oriented
High sensitivity and baseline stability matter more than a wide full-scale range.
- 4-electrode electrochemical
- Low-noise AFE and temperature compensation
10–200 ppm typical design space
Moisture and condensation often dominate the mechanical design. Use a gas sensor only when measuring the gas phase, not by immersing the cell.
- Diffusion or pumped headspace sampling
- Condensate control is essential
2,000–10,000 ppm class
Raw process gas can exceed the range of personal-safety cells. Extended-range electrochemical sensors or dedicated process analyzers are more appropriate.
- High overload capacity
- Hydrogen compensation may matter
UART / conditioned module
Use a module when the controller needs gas concentration directly or when several hazards are combined in one portable detector.
- Single-gas smart H₂S
- CO + H₂S + O₂ + CH₄ modules
Electrochemical is the main H₂S route, but package and electronics change the result
Most dedicated H₂S safety sensors are amperometric electrochemical cells. Gas diffuses to the working electrode, the H₂S reaction produces a current, and the instrument converts that current into concentration. The cell is only one part of the measurement chain.
3-electrode EC
The standard architecture for portable and fixed toxic-gas instruments. The reference electrode controls working-electrode potential.
Best fit: worker safety and fixed detection.4-electrode EC
An auxiliary electrode provides a second baseline signal that can be used for low-level compensation.
Best fit: fenceline, air quality and low-ppm monitoring.Smart / conditioned EC
The electrochemical cell is combined with AFE, temperature compensation and digital or analog output.
Best fit: shorter OEM development cycles.MEMS / MOX
A heated metal-oxide layer changes resistance in H₂S. It is compact and low cost, but selectivity and heater behavior differ from electrochemical cells.
Best fit: embedded or non-equivalent alternative designs.H₂S sensors for different OEM requirements
The shortlist mixes portable, fixed, low-level, high-temperature, high-range and digital routes. Compare products only against the job they are intended to do.
| OEM need | Manufacturer | Model | Type | Published range | Key engineering point | Official source |
|---|---|---|---|---|---|---|
| Miniature digital industrial H₂S | Winsen | SME100-H₂S | Intelligent electrochemical | 0.5–200 ppm | UART, 0.1 ppm resolution, T90 <30 s, 5-year expected life in air; flat ~1 cm platform. | Official ↗ |
| Fast portable / fixed safety | Winsen | MEu-H₂S | Electrochemical | 0–100 ppm max 500 ppm | T90 <15 s on the current product page; compact raw cell for portable and fixed instruments. | Official ↗ |
| Miniature personal monitor | Alphasense | H2S-D4 | D-Series electrochemical | 0–100 ppm | Miniature clip-on format, T90 <25 s, 24-month warranty. | Official ↗ |
| Portable 4-Series life safety | Honeywell City Technology | 4HS+ | 3-electrode electrochemical | 0–100 ppm max overload 500 ppm | 20 s T90, low SO₂ cross-sensitivity positioning, standard 4-Series package. | Datasheet ↗ |
| Fixed industrial / wastewater | SENKO | SS4198 | Electrochemical | 0–200 ppm max overload 1,000 ppm | T90 <35 s, <0.1 ppm typical resolution, >24-month expected life. | Official ↗ |
| High-temperature fixed detector | SENKO | SS4198-HT | Electrochemical | 0–100 ppm max overload 500 ppm | T90 <20 s and continuous operation up to +70°C on the current product page. | Official ↗ |
| Low-level environmental / fenceline | Alphasense | H2S-A41 | 4-electrode electrochemical | 0–50 ppm | High-output ppb-capable A4 platform with auxiliary electrode for baseline compensation. | Official ↗ |
| Biogas / extended process range | Alphasense | H2S-BE | B-Series electrochemical | 0–2,000 ppm | Extended-range fixed/process cell, T90 <50 s; positioned for biogas and high-concentration process monitoring. | Official ↗ |
| Raw biogas / very high range | Membrapor | H2S/CG-10000 | Compact electrochemical | 10,000 ppm class | Gas-tight compact H₂S family; Membrapor specifically recommends the CG series for biogas and landfill gas. | Official ↗ |
| 4-gas portable OEM | Winsen | ZCE04B | Multi-gas module | H₂S 0–100 ppm | CO + H₂S + O₂ + CH₄ in one UART module; H₂S resolution 1 ppm, response <30 s. | Official ↗ |
Component specifications are not finished-instrument performance. Confirm the latest datasheet, cross-sensitivity table, gas path and applicable detector standard before design freeze.
H₂S sensor priorities change with the site
Portable and confined-space safety
Fast response, small size and reliable recovery after an exposure pulse are the main design checks.
| Model | Range | T90 | What to check |
|---|---|---|---|
| Winsen MEu-H₂S | 0–100 ppm | <15 s | Fast raw electrochemical route; verify current gas-specific datasheet before design-in. |
| Alphasense H2S-D4 | 0–100 ppm | <25 s | Miniature D-Series package for clip-on personal monitors. |
| Honeywell 4HS+ | 0–100 ppm | 20 s | 4-Series footprint with published cross-sensitivity guidance. |
Fixed industrial and wastewater headspace
Long-term humidity, enclosure diffusion, corrosion, calibration access and condensate management matter as much as the sensor range.
| Model | Range | Environmental point | Best fit |
|---|---|---|---|
| Winsen ME4-H₂S | 0–100 ppm | -20 to 50°C, 15–90%RH non-condensing | Standard industrial / mining / environmental detection. |
| SENKO SS4198 | 0–200 ppm | 15–90%RH; max overload 1,000 ppm | Petrochemical, wastewater, mining and fixed instruments. |
| SENKO SS4198-HT | 0–100 ppm | Continuous -20 to +70°C | High-temperature, low-humidity fixed installations. |
Low-level odor and environmental monitoring
Low concentration requires a stable zero. High full-scale range is not useful if the baseline and electronics noise are larger than the signal you want to resolve.
| Model / route | Range | Architecture | Engineering reason |
|---|---|---|---|
| Alphasense H2S-A41 | 0–50 ppm | 4-electrode | High sensitivity, ppb-oriented monitoring and baseline compensation. |
| Alphasense H2S-B4 | 0–100 ppm | 4-electrode B-Series | Larger fixed-monitor format for ppb-level environmental and fenceline work. |
| Dedicated air-quality monitor | Often 0–10 ppm class | Conditioned system | Useful when factory calibration, very low MDL and environmental correction are required. |
Biogas and high-range process H₂S
Raw biogas can move far beyond a normal personal-safety sensor range. High H₂S exposure also increases the importance of sample conditioning and recovery behavior.
| Model / family | Range class | Process feature | Official source |
|---|---|---|---|
| Alphasense H2S-BE | 0–2,000 ppm | Extended-range fixed/process cell. | Official ↗ |
| Membrapor H2S/CG-2000 | 2,000 ppm class | Gas-tight compact family for biogas/process service. | Official ↗ |
| Membrapor H2S/CG-5000 | 5,000 ppm class | Higher-range biogas/process option. | Official ↗ |
| Membrapor H2S/CG-10000 | 10,000 ppm class | Very high-range route; compare against a dedicated process analyzer where continuous accuracy is critical. | Official ↗ |
What usually causes H₂S measurement problems
Overload and recovery
A sensor can survive a concentration above its measurement range and still be unusable for accurate measurement during or immediately after that exposure.
- Compare measurement range and maximum overload separately.
- Ask how quickly the cell returns to baseline after a high H₂S pulse.
- For process streams, estimate both peak concentration and exposure duration.
Moisture and condensation
Wastewater, sewer gas and biogas are often humid. Most electrochemical specifications allow high RH but explicitly exclude condensation.
- Keep liquid water away from the diffusion opening.
- Use drain legs, filters, heated lines or moisture separation where pumped sampling requires them.
- A long wet sample tube can change response time and gas delivery even if the sensor itself is healthy.
Cross-sensitivity
CO, H₂, SO₂, NO, NO₂, Cl₂ and other gases can produce positive or negative readings depending on the cell chemistry and filter.
- Use the exact model cross-sensitivity table.
- Do not transfer correction factors from a similar package or older sensor revision.
- Hydrogen-compensated 4-electrode H₂S products are available for biogas and mixed-gas applications.
Sulfur exposure and sensitivity
H₂S electrochemistry can form sulfur species at the electrode. High cumulative exposure can affect sensitivity and recovery depending on sensor design.
- Do not size a 100 ppm safety cell for a process that routinely sees thousands of ppm.
- Track calibration drift where exposure is frequent.
- Replace a cell that cannot recover its baseline or span response after the required conditioning procedure.
Decide what phase you are measuring before choosing the sensor
“H₂S in wastewater” can mean three different measurements: headspace gas, extracted gas from a liquid sample, or dissolved sulfide in the liquid. A standard gas sensor only measures gas reaching its diffusion path.
Define the phase
Gas-phase headspace, pumped sample gas, or dissolved sulfide.
Estimate the range
Normal ppm, alarm region and credible upset concentration.
Manage water
Prevent condensate from blocking tubing, filters or the sensor inlet.
Verify response
Test the complete sampling path; tubing delay can dominate the sensor T90.
Raw biogas often needs a different measurement architecture
Personnel safety around a digester and H₂S concentration inside the biogas line are two different tasks. Area safety may use a conventional 0–100/200 ppm cell, while process control can require 2,000–10,000 ppm range and a conditioned sample.
Area / personnel safety
- Use a conventional toxic-gas H₂S cell around the worker breathing zone or fixed hazard area.
- Prioritize fast response, alarm reliability and routine bump testing.
- Range is usually far lower than the raw process stream.
Process gas measurement
- Use an extended-range electrochemical cell or dedicated process analyzer.
- Condition moisture and condensate before the sensing element when required.
- Review H₂ compensation where hydrogen is present in the gas mixture.
Raw H₂S sensor, smart sensor or multi-gas module?
Choose a raw electrochemical element when:
- Your team controls the potentiostat / transimpedance circuit.
- You need the lowest component cost at volume.
- You want full control over temperature compensation and calibration.
- The gas path and mechanical footprint are already defined.
Choose a smart sensor or module when:
- Your MCU needs UART or conditioned analog output.
- Development time matters more than minimum BOM cost.
- You want calibration and signal conditioning handled in the sensor assembly.
- You are building a multi-gas portable instrument around CO / H₂S / O₂ / CH₄.
Additional Winsen H₂S formats and modules
The products below cover standard electrochemical elements, digital modules, multi-gas platforms and MEMS routes. They should not be treated as interchangeable simply because they respond to H₂S.
SME100-H₂S / SMX100
0.5–200 ppm, 0.1 ppm resolution, T90 <30 s, UART output and a 5-year expected lifetime in air. Suitable for compact industrial OEM designs.
MEu-H₂S
The current product page lists 0–100 ppm, maximum 500 ppm and T90 <15 s. Use the current revision-controlled datasheet when freezing the design.
ME4-H₂S
0–100 ppm, maximum 500 ppm, 0.1 ppm resolution, T90 <30 s and a 2-year published life in air. Used for industrial, mining and environmental detection.
ME3-H₂S
0–100 ppm, maximum 500 ppm, 0.1 ppm resolution and T90 <30 s in a smaller electrochemical package.
ZE03-H₂S configuration
Three-electrode electrochemical module with UART and analog voltage output. The current product page directs users to the gas-specific manual for the measurement range.
ZCE04B
CO 0–1,000 ppm, H₂S 0–100 ppm, O₂ 0–30%vol and CH₄ 0–100%LEL in one UART module. H₂S resolution is 1 ppm.
GM-602B
MEMS metal-oxide sensor with a published H₂S range of 0.5–50 ppm and heater consumption ≤40 mW. Also responds to benzene and should be evaluated as a different sensing route from electrochemical safety cells.
GM-512B
0.5–50 ppm H₂S range in a MEMS breath-odor sensor that is also sensitive to alcohol and acetone. Its intended application is mini breath detection, not a dedicated industrial H₂S safety channel.
Other H₂S sensor product ranges
These manufacturers publish H₂S sensors for portable safety, fixed monitoring, environmental measurement, process gas or digital OEM use.
Alphasense
Miniature, fixed, 4-electrode, dual-gas and extended-range electrochemical H₂S sensors.
Honeywell City Technology
4-Series H₂S cells for portable and fixed life-safety equipment.
Membrapor
Compact, slim and high-range H₂S sensors, including biogas and H₂-compensated variants.
SENKO
Portable/fixed H₂S electrochemical sensors including high-temperature versions.
Nemoto
Electrochemical toxic-gas sensors and specialist H₂S formats.
SGX Sensortech
Electrochemical and digital H₂S formats available through the official selector.
H₂S sensors need a maintenance plan, not only a lifespan figure
Published life values are useful for replacement planning, but field exposure, humidity, temperature, contaminants and cumulative H₂S dose can move the real service interval in either direction.
Bump test
Confirm that H₂S reaches the sensor, the channel responds and the alarms operate. A bump test is a functional check, not a full accuracy calibration.
Calibration
Apply a known H₂S concentration to establish or adjust response. Follow the finished instrument procedure and site requirements.
Replacement criteria
Replace or service the sensor when span sensitivity, baseline recovery or response time no longer meets the instrument specification.
Hydrogen sulfide sensor questions
What H₂S sensor range is typical for personal safety instruments?
A 0–100 ppm or 0–200 ppm electrochemical cell is common for portable and fixed toxic-gas safety instruments. The final choice depends on alarm strategy, expected peak exposure, overload recovery, response time and the finished detector standard.
When do I need a high-range H₂S sensor?
Use an extended-range sensor when the process gas can exceed the normal safety range. Raw biogas, landfill gas and sour process streams can reach hundreds or thousands of ppm, so a 0–100 ppm personal-safety cell may saturate or recover too slowly after exposure.
Why are 4-electrode H₂S sensors used for environmental monitoring?
The auxiliary electrode provides a second baseline signal that can be used to compensate zero changes. That is useful when the target is low ppm or ppb-level H₂S and the signal must be separated from temperature-related baseline movement and electronic noise.
Can I use a gas-phase H₂S sensor directly in wastewater?
Not usually. Standard electrochemical gas cells are designed for gas reaching a diffusion path and must not be immersed. For wastewater projects, decide whether you are measuring headspace H₂S, extracted gas, or dissolved sulfide in the liquid. Direct in-liquid monitoring requires a dedicated probe or sampling method.
What cross-sensitivities matter for H₂S electrochemical sensors?
Check the exact model datasheet for SO₂, CO, H₂, NO, NO₂, Cl₂ and other gases expected at the site. Cross-sensitivity varies by chemistry, filter and electrode design; it should not be assumed from another sensor in the same package.
Should I choose a raw H₂S cell or a module?
Choose a raw electrochemical element when your team will design the analog front end, temperature compensation and calibration. Choose a module when UART or analog output, factory conditioning and a shorter integration cycle are more valuable.
How does high humidity affect H₂S measurement?
Humidity affects both the sensor and the gas path. Most electrochemical H₂S sensors specify a non-condensing RH range. Condensation can block diffusion paths, change sample transport and damage electronics, so wastewater and biogas systems need moisture management.
What is the difference between a bump test and calibration for H₂S?
A bump test checks that gas reaches the sensor and that the instrument responds and alarms. Calibration applies a known H₂S concentration to establish or adjust measurement accuracy. Both procedures should follow the finished instrument and site maintenance requirements.
Final checks before design freeze
Use the current product datasheet as the final component reference, then validate the complete instrument under the expected H₂S concentration, gas mixture, humidity and sample path.
- Confirm measurement range and maximum overload separately.
- Review T90, baseline recovery and expected exposure duration.
- Check CO, H₂, SO₂, NOx, Cl₂ and other relevant cross-sensitivities.
- Keep condensation away from gas sensor diffusion paths.
- Validate calibration gas delivery through the actual enclosure or sampling line.
- Confirm the finished detector standard and certification requirements for the target market.
Need an H₂S sensor for an OEM project?
Send the target range, application, expected peak concentration, operating environment, output interface and product format. Manufacturers can also submit H₂S sensor models with an official product page and current datasheet.
Specifications and product availability can change. Confirm the latest manufacturer datasheet before engineering, compliance or purchasing decisions.