High-performance NO detection for portable, fixed and miniature gas monitors

Alphasense nitric oxide (NO) sensors support general and industrial safety, emissions monitoring and air quality applications. Available in A, B, D and H series formats and ppb-level 4-electrode variants, they give OEMs flexible options for portable analyzers, fixed installations and compact personal safety instruments.

Sensor Portfolio Overview


Portable & Industrial Safety – A-Series NO Sensors


  • NO-A1 – Standard A-Series NO sensor (0–250 ppm) 
    Electrochemical NO sensor with +300 mV bias for general and industrial safety and emissions monitoring where typical NO levels are up to 250 ppm. Compact A-series format is ideal for handheld and portable instruments
  • NO-A41 – A-Series 4-electrode ppb NO sensor
    • A-series 4-pin ppb NO sensor with +200 mV bias for air quality, portable and handheld instruments. Four-electrode architecture improves baseline stability and low-level performance.
  • NO-AE – Extended-range A-Series (up to 5000 ppm NO)
    • High-concentration A-series NO sensor for applications where very high NO levels must be measured. 0–5000 ppm range with +300 mV bias, used in industrial safety, combustion and emissions monitoring where extended range is required.

Fixed Monitoring & High-Humidity – B-Series NO Sensors


  • NO-B1 – Standard B-Series NO sensor (0–250 ppm)
    • Electrochemical NO sensor in the larger B-series format for fixed installations. 0–250ppm range with +300 mV bias, suitable for general and industrial safety in high-humidity or outdoor environments.
  • NO-B4 – B-Series 4-electrode ppb NO sensor
    • B-series 4-pin ppb NO sensor with +200 mV bias, widely used in fixed air quality and atmospheric monitoring. The larger B-series format and four-electrode design deliver very low noise and good performance in high humidity.

Miniature & Wearable – D-Series and H-Series NO Sensors


  • NO-D4 – Miniature D-Series NO sensor
    • Small-format electrochemical NO sensor (0–100 ppm with +300 mV bias) for clip devices, handheld instruments and space-constrained portable monitors. Designed for personal and industrial safety.
  • NO-H4 – H-Series NO sensor
    • Miniature NO sensor (0–100 ppm with +300 mV bias) in the H-series package for clipped and personal instruments where space is limited. Suitable for personal safety devices.

Integrated Smart Technology (IST) NO Sensor Versions


    Many NO sensors are available with Integrated Smart Technology (IST), adding on-sensor electronics and digital features to simplify OEM integration. IST variants (A+ and B+ series) are directly related to their analogue counterparts, for example:
  • NO-A1-IST – related to NO-A1
  • NO-AE-IST – related to NO-AE
  • NO-B1-IST – related to NO-B1
  • NO-A41-IST – related to NO-A41
  • NO-B4-IST – related to NO-B4
    IST versions typically provide:
  • On-sensor electronics with a digital output
  • Storage of factory calibration data
  • Simplified board-level design and integration
  • Plug-and-play sensor replacement

Choosing the Right NO Sensor by Application General industrial safety (portable / personal):


  • NO-A1 – A-series sensor for handheld and portable safety and emissions monitors up to 250 ppm
  • NO-D4, NO-H4 – miniature sensors for clip devices, personal detectors and other space-constrained portable instruments

Fixed installations & high-humidity environments:


  • NO-B1 – B-series sensor for fixed systems in general and industrial safety applications, suitable for high humidity
  • NO-B4 – ppb-level B-series sensor for fixed air quality and atmospheric monitoring

High-range NO / process & emissions:


  • NO-AE – extended-range A-series sensor (0–5000 ppm) for industrial safety, process control and emissions monitoring where high NO levels are present

Air quality & PPB-level monitoring:


  • NO-A41 – A-series 4-electrode ppb NO sensor for portable and handheld air quality analyzers
  • NO-B4 – B-series 4-electrode ppb NO sensor for fixed air quality networks and long-term monitoring

Key Benefits Across the NO Sensor Portfolio


  • Multiple form factors (A, B, D, H) to suit portable, fixed, wearable and OEM-specific instruments
  • Standard and extended-range options to match typical and high-concentration NO applications
  • PPB-level, 4-electrode NO sensors (NO-A41, NO-B4) for advanced air quality and low-level monitoring
  • Miniature D- and H-series options (NO-D4, NO-H4) for clip-on and personal safety devices
  • IST digital variants (NO-A1-IST, NO-AE-IST, NO-B1-IST, NO-A41-IST, NO-B4-IST)that simplify integration and calibration handling

Why OEMs Choose Alphasense


Alphasense nitric oxide sensors are built on proven electrochemical platforms used across multiple toxic gas families. The portfolio combines:

  • Broad coverage from ppm safety sensors to ppb-level air quality sensors
  • Multiple mechanical formats for portable, fixed and wearable devices
  • Strong technical support and compatible analogue front-end / ISB boards for 4-electrode sensors
  • Long product lifecycles and consistent manufacturing to support stable instrument designs over time

How NO Sensors Work


Alphasense NO sensors use electrochemical amperometric technology to convert nitric oxide concentration into a measurable electrical signal. Each sensor contains an electrochemical cell where NO participates in a controlled reaction at the working electrode. The reaction rate is proportional to the NO concentration at the electrode surface.

In three-electrode sensors, the working, reference and counter electrodes are arranged so that a potentiostat can hold the working electrode at the required bias (for example +300mV or +200 mV, depending on the sensor type) and measure the resulting current. This current is proportional to gas concentration.

In four-electrode ppb sensors (such as NO-A41 and NO-B4), an auxiliary electrode is added to improve zero-current stability and temperature compensation, which is critical for low-level air quality measurements.

The resulting current (or derived voltage) is read by the instrument’s analogue front end or digital electronics, and calibration data are applied to display NO readings to the user.

Why Measure NO Gas?

Monitoring nitric oxide (NO) is essential for protecting workers and maintaining safe industrial environments, as NO is a toxic gas that can cause serious respiratory harm when present at elevated levels. Measuring NO also supports environmental compliance and emissions control by identifying combustion inefficiencies, pollution sources, and equipment faults across industrial and mobile applications. Accurate NO detection enables OEMs and safety professionals to improve process performance, maintain regulatory standards, and ensure reliable air quality monitoring across both portable and fixed instruments.

From industrial leak detection to occupational health and safety monitoring, measuring NO is critical for preventing toxic exposure and ensuring environmental compliance.

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