High-Performance H2S Detection for Every Monitor, Every Mission.
Alphasense offers the industry’s most complete H2S sensor portfolio—covering portable safety, fixed installations, dual-gas configurations, PPB-level air-quality monitoring, and compact miniature designs. Built on proven electrochemical platforms, these sensors deliver fast response, excellent stability, and long operational life across challenging industrial environments.
Sensor Portfolio Overview
Portable & Industrial Safety – A-Series
Robust, field-proven sensors ideal for hand-held and portable monitors.- H2S-A1 – Standard 0–100 ppm detection for general industrial and worker safety.
- H2S-AE – Extended-range 0–2000 ppm for process, high-level, and upset-condition monitoring.
- H2S-AH – High-output 0–50 ppm sensor for high-resolution, low-ppm detection.
- H2S-A41 – PPB-level, 4-electrode A-Series sensor for air-quality and ultra-low detection needs.
Fixed Gas Monitoring – B-Series
Designed for stationary systems requiring long life, high stability, and robust environmental resistance.- H2S-B1 – Standard 0–200 ppm for fixed instrumentation in industrial and municipal applications.
- H2S-BE – Extended-range 0–2000 ppm; ideal for biogas, wastewater, and harsh-environment process monitoring.
- H2S-BH – High-output 0–50 ppm for precision low-range fixed detection.
- H2S-B4 – PPB-level detection for fixed air-quality and atmospheric monitoring applications.
Miniature & Wearable – D-Series and H-Series
Ultra-compact formats for clip-on personal detectors and space-constrained designs.- H2S-D4 – 0–100 ppm, miniature format, fast response for personal safety devices.
Purpose-built for specific OEM requirements and compact wearable instruments.
- H2S-H4 – H-Series package for high-volume portable devices.
Dual Gas H₂S Sensors – Space Saving Safety Monitoring
Ideal where footprint, cost, and board space are limited.CO + H2S Dual Sensors
- COH-A2 – A-Series dual CO (0–1000 ppm) + H2S (0–100 ppm) sensor.
- COH-D2 – Miniature D-Series dual CO + H2S with high-capacity filter for reliable long-term performance.
- COH-H2 – H-Series dual configuration for compact Honeywell-format instruments.
- SOH-A2 – Measures both SO2 (0–20 ppm) and H2S (0–100 ppm) simultaneously for corrosion-gas discrimination.
Integrated Smart Technology (IST) Versions
Most H₂S sensors listed above are also available with IST—Integrated Smart Technology—providing:- On-sensor electronics for digital output of calibration data and sensor temperature
- Factory calibration storage
- Simplified integration for OEMs
- Plug and play operation
COH-A2-IST | H2S-A1-IST | H2S-A41-IST | H2S-AE-IST | H2S-AH-IST | H2S-B1-IST | H2S-B4-IST | H2S-BE-IST | H2S-BH-IST | SOH-A2-IST
Choosing the Right H2S Sensor
High-Resolution / Low-Range (0–50 ppm) General Industrial Safety (0–100 / 0–200 ppm) High-Range / Process (up to 2000 ppm) Ultra-Low / PPB Detection Dual Gas / Space-Constrained
Key Benefits Across the H2S Portfolio
- Fast T90 for rapid worker-safety alarms
- Excellent stability across humidity and temperature extremes
- Low cross-sensitivities in demanding industrial environments
- Long-life designs reduce maintenance cost for OEMs and end-users
- Multiple mechanical formats to fit any instrument architecture
Why OEMs Choose Alphasense
With decades of performance data and millions of sensors deployed globally, Alphasense H2S sensors are trusted for:- Reliable performance in real-world harsh conditions
- Consistent batch-to-batch output
- Strong technical support and long product lifecycles
- Broadest portfolio of formats and performance classes
How H2S Sensors Work
Alphasense H2S sensors use electrochemical amperometric technology to convert H2S gas concentration into a measurable electrical signal.- Electrochemical cell Each sensor contains an electrochemical cell where H2S participates in a controlled reaction at the working electrode. The sensor is designed so that the reaction rate is proportional to the HS concentration at the electrode surface.
- Amperometric measurement Amperometric sensors operate by measuring the current produced by the electrochemical reaction at the working electrode. An external potentiostat circuit is required to measure the current between the working electrode, counter electrode and reference electrode.
- Working electrode – designed to optimise the oxidation or reduction of the toxic gas to be measured.
- Reference electrode – keeps working electrode at required potential – Bias voltage.
- Counter electrode – balances the reaction of the working electrode
- Auxiliary electrode - Baseline correction for Zero Current and Temperature shifts that are critical for PPB sensors
- Signal output to the instrument The resulting current (or corresponding voltage, depending on the front-end electronics) is proportional to the HS concentration. This signal is then read by the instrument’s analogue front-end or digital electronics which apply calibration data to display H2S readings to the user.
- Filtering and cross-sensitivity control The H2S sensors incorporate internal filters and/or specific electrode designs to reduce cross-sensitivities to other gases such as CO, NO, NO SO and H.
In a three-electrode sensor, each electrode has a specific use: