Reliable NO2 detection for portable, fixed and miniature gas monitors.

Alphasense nitrogen dioxide (NO2) sensors cover general and industrial safety, HVAC, emissions and air quality monitoring. Available in A, B, D and H series formats and filtered 4-electrode ppb variants, they support handheld instruments, fixed installations and compact personal safety devices


Sensor Portfolio Overview


Portable & Industrial Safety – A-Series NO2 Sensors


  • NO2-A1 – Standard A-Series NO2 sensor (0–20 ppm)
    • Electrochemical A-series NO2 sensor for handheld and portable instruments. 0–20 ppm range for general and industrial safety, HVAC and mining applications requiring good resolution at low NO2 levels.
  • NO2-A43F – A-Series filtered 4-electrode ppb NO2 sensor
    • A-series 4-pin ppb NO2 sensor with internal filtering to reduce ozone (O3) cross sensitivity to zero. Used in portable and handheld air quality instruments worldwide where accurate low-level NO2 measurement is required.
  • NO2-AE – Extended-range A-Series (up to 200 ppm NO2)
    • Extended-range NO2 sensor (0–200 ppm, successfully used up to 1000 ppm in some applications) for emissions, general and industrial safety where higher NO2 levels must be measured.

Fixed Monitoring & High-Humidity – B-Series NO2 Sensors


  • NO2-B1 – Standard B-Series NO2 sensor (0–20 ppm)
    • Electrochemical NO2 sensor for fixed applications, with 0–20 ppm range. Suitable for general and industrial safety and HVAC monitoring, including high-humidity environments.
  • NO2-B43F – B-Series filtered 4-electrode
    • PPB NO2 sensor B-series 4-pin ppb NO2 sensor with the same O3-rejection filtering, mainly used in fixed air quality installations. Widely deployed in air quality devices and suitable for high-humidity environments.

Miniature & Wearable – D-Series and H-Series NO2 Sensors


  • NO2-D4 – Miniature D-Series NO2 sensor
    • Small-format electrochemical NO2 sensor (0–20 ppm) for clip devices, handheld instruments and personal safety monitors.
  • NO2-H4 – Compact H-Series NO2 sensor
    • Miniature NO2 sensor (0–20 ppm) in the H-series package for clipped and personal instruments where space is limited, supporting personal safety applications.

Integrated Smart Technology (IST) NO2 Sensor Versions


    Many NO2 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:
  • NO2-A1-IST – related to NO2-A1
  • NO2-AE-IST – related to NO2-AE
  • NO2-B1-IST – related to NO2-B1
  • NO2-A43F-IST – related to NO2-A43F
  • NO2-B43F-IST – related to NO2-B43F
    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 NO2 Sensor by Application



General industrial safety & HVAC (portable / personal):


  • NO2-A1 – A-series sensor for handheld and portable safety / HVAC monitors up to 20 ppm
  • NO2-D4, NO2-H4 – miniature sensors for clip and personal devices where space is limited

Fixed installations & high-humidity environments:


  • NO2-B1 – B-series sensor for fixed safety and HVAC systems in high-humidity or outdoor environments
  • NO2-B43F – B-series ppb sensor for fixed air quality networks and long-term monitoring

Emissions & high-range NO2:


  • NO2-AE – extended-range A-series sensor (0–200 ppm, used up to 1000 ppm in some applications) for emissions and industrial safety where higher NO2 levels must be measured

Air quality & ppb-level monitoring:


  • NO2-A43F – filtered A-series 4-electrode NO2 sensor for portable and handheld air quality analyzers, with O3 cross sensitivity reduced to zero
  • NO2-B43F – filtered B-series 4-electrode NO2 sensor for fixed air quality devices and high-humidity environments

Key Benefits Across the NO2 Sensor Portfolio


  • Multiple form factors (A, B, D, H) to cover portable, fixed, wearable and OEM-specific instruments
  • Standard and extended-range options to support safety, HVAC and emissions monitoring
  • Filtered 4-electrode NO2 sensors (NO2-A43F, NO2-B43F) with O3 cross sensitivity reduced to zero for accurate low-level air quality measurements
  • Miniature D- and H-series options (NO2-D4, NO2-H4) for clip-on and personal safety devices
  • IST digital variants (NO2-A1-IST, NO2-AE-IST, NO2-B1-IST, NO2-A43F-IST, NO2-B43F-IST) that simplify integration and calibration handling

Why OEMs Choose Alphasense


Alphasense nitrogen dioxide sensors leverage proven electrochemical platforms shared across multiple toxic gas families. OEMs benefit from:

  • Broad portfolio coverage from ppm safety sensors to ppb-level air quality sensors
  • Mechanical formats suited to portable, fixed and wearable devices
  • Strong technical support and dedicated front-end boards for 4-electrode sensors
  • Long product lifecycles and consistent manufacturing that support stable instrument designs

How NO2 Sensors Work


Alphasense NO2 sensors use electrochemical amperometric technology to convert nitrogen dioxide concentration into a measurable electrical signal. Each sensor contains an electrochemical cell where NO2 participates in a controlled reaction at the working electrode. The reaction rate is proportional to the NO2 concentration at the electrode surface.

Three-electrode sensors use a working, reference and counter electrode with a potentiostat to hold the working electrode at the required potential and measure the resulting current. This current is proportional to gas concentration.

Filtered 4-electrode ppb sensors (such as NO2-A43F and NO2-B43F) add an auxiliary electrode for improved baseline stability and temperature compensation, and include internal filtering to eliminate O3 cross sensitivity. 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 NO2 readings to the user.

Why Measure NO2 Gas


Nitrogen dioxide (NO2) monitoring is critical for air quality assessment, health protection, and regulatory compliance. NO2 is a combustion byproduct from vehicular and industrial sources and is classified as a criteria air pollutant.

  • Health Effects:
     Acute and chronic exposure to NO2 causes airway inflammation, exacerbates asthma, reduces pulmonary function, and can result in irreversible lung damage.
  • Environmental Effects:
    Atmospheric NO2 participates in photochemical reactions that form ground-level ozone and nitric acid, contributing to smog, acid rain, ecosystem degradation and reduced visibility.
  • Indoor and Occupational Safety:
    Poorly ventilated residential and industrial environments with combustion appliances require NO2 monitoring to prevent hazardous indoor accumulation.
  • Emissions and Traffic
    Monitoring: Ambient NO2 levels serve as a proxy for combustion-related emissions, enabling identification of traffic-related pollution hotspots and evaluation of emission control strategies.
Continuous NO2 sensing is therefore essential in urban, industrial and indoor environments to ensure safety, environmental protection and compliance with air quality standards.

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