Nitrogen Dioxide Sensors
Select NO₂ sensors for worker safety, diesel and traffic monitoring, tunnels and garages, ambient air quality, HVAC and combustion or emissions equipment. Compare ppm safety cells, filtered 4-electrode ppb sensors, environmental modules and high-range options.
Choose the NO₂ sensor around the source and concentration
Nitrogen dioxide appears in occupational environments, diesel exhaust, roadway pollution and combustion systems. Range and sensor architecture should follow the measurement task rather than a single universal NO₂ specification.
0–20 ppm
Compact 3-electrode electrochemical cells are the standard route for personal and handheld NO₂ instruments.
- Fast T90
- Small package and low noise
0–20 / 50 ppm
Fixed transmitters need stable long-term baseline, humidity tolerance and a gas path that represents the local hazard.
- Industrial and mining areas
- Combustion equipment rooms
Low ppm / sub-ppm
Traffic-related NO₂ monitoring benefits from stable low-level response and attention to ozone cross-sensitivity.
- Roadside nodes
- Diesel vehicle and tunnel monitoring
0–1 ppm / ppb-oriented
Use filtered 4-electrode sensors or conditioned modules when ppb baseline stability is required.
- Urban background
- Fenceline / environmental monitoring
0–200 ppm and above
High-range NO₂ cells can be part of a flue-gas analyzer, but total NOx measurement often also requires an NO channel.
- Boilers / burners
- Emissions and combustion analysis
Multi-parameter module
NO₂ can be combined with CO₂, PM, O₃, CO, VOC and temperature/humidity in building-control equipment.
- UART integration
- Ventilation and air-quality products
3-electrode for ppm NO₂, filtered 4-electrode for ppb air quality
Compact NO₂ sensors are commonly amperometric electrochemical cells. Nitrogen dioxide is reduced at the working electrode and produces a concentration-related current. The instrument's analog front end converts that current into a calibrated concentration.
3-electrode EC
The normal route for portable and fixed NO₂ safety instruments.
Best fit: ppm industrial detection.4-electrode EC
An auxiliary electrode supplies baseline information for temperature and environmental correction.
Best fit: ppb roadside and ambient monitoring.O₃-filtered NO₂
Internal filtering removes or strongly reduces ozone before it reaches the NO₂ sensing electrode.
Best fit: urban air-quality measurement.Conditioned module
The cell, AFE, temperature correction and UART / analog interface are integrated into one assembly.
Best fit: environmental and IAQ OEM projects.NO₂ sensors for safety, roadside, ambient and emissions designs
The shortlist mixes general safety sensors, miniature personal-monitor cells, filtered ppb products, digital environmental modules and extended-range emissions options.
| OEM need | Manufacturer | Model | Type | Published range | Key engineering point | Official source |
|---|---|---|---|---|---|---|
| General portable / fixed NO₂ | Winsen | ZE03-NO₂ | Electrochemical module | 0–20 ppm | 0.1 ppm resolution, T90 ≤30 s in the current ZE03 manual, UART plus analog voltage output. | Official ↗ |
| Standard industrial safety | Alphasense | NO2-A1 | 3-electrode electrochemical | 0–20 ppm | T90 <50 s, low zero current and A-Series format for portable / fixed safety and HVAC instruments. | Official ↗ |
| Miniature personal monitor | Alphasense | NO2-D4 | Miniature 3-electrode EC | 0–20 ppm | T90 <35 s and compact D-Series package for clip-on and wearable detectors. | Official ↗ |
| Garage / diesel / portable ambient | SENKO | SS2148 | Electrochemical | 0–20 ppm max overload 40 ppm | T90 <30 s, <0.1 ppm typical resolution; published for garage ventilation and diesel-vehicle monitoring. | Official ↗ |
| PPB fixed roadside / urban monitoring | Alphasense | NO2-B43F | Filtered 4-electrode EC | 0–20 ppm | PPB-level resolution, ozone-rejection filtering, T90 <80 s and B-Series stability for fixed outdoor networks. | Official ↗ |
| Conditioned ambient NO₂ | Winsen | ZE12A-NO₂ | Electrochemical module | 0–1 ppm | ≤10 ppb resolution, DAC + UART, built-in temperature compensation and T90 ≤120 s. | Official ↗ |
| Multi-pollutant outdoor station | Winsen | ZEHS04 | Multi-gas EC module | NO₂ + CO + SO₂ + O₃ | UART / RS485, ≤10 ppb published gas resolution, optional PM and temperature/humidity expansion. | Official ↗ |
| IAQ / HVAC multi-sensor | Winsen | ZPHS01B | Multi-in-one air-quality module | NO₂ 0.1–10 ppm | 0.05 ppm NO₂ resolution; combines CO₂, PM2.5, CH₂O, O₃, CO, TVOC, NO₂, temperature and humidity over UART. | Official ↗ |
| High-range emissions NO₂ | Alphasense | NO2-AE | 3-electrode electrochemical | 0–200 ppm | T90 <40 s; official product page notes successful use up to 1,000 ppm in some applications. | Official ↗ |
| Flue-gas analyzer route | Honeywell City Technology | 5ND | 5-Series electrochemical | 0–200 ppm class | 5-Series NO₂ cell for combustion / flue-gas analyzer platforms; use current 5ND datasheet for final overload and bias requirements. | 5-Series ↗ |
Published values are component or module data. Confirm the current datasheet, bias/polarity, ozone response, temperature behavior and finished-instrument requirements before design freeze.
NO₂ sensor priorities change with the source
Portable and fixed industrial safety
Worker-safety channels need reliable ppm response, predictable interference behavior and an enclosure that exposes the cell to the local atmosphere quickly.
| Product | Range | T90 | Engineering point |
|---|---|---|---|
| Winsen ZE03-NO₂ | 0–20 ppm | ≤30 s | Conditioned UART / analog module for portable or fixed OEM instruments. |
| Alphasense NO2-A1 | 0–20 ppm | <50 s | Raw A-Series safety cell with low zero current. |
| SENKO SS2148 | 0–20 ppm | <30 s | Fast sensor with direct positioning for diesel and garage monitoring. |
Roadside, tunnel and diesel monitoring
Traffic combustion produces both NO and NO₂. Near roads and diesel sources, the useful NO₂ signal can change quickly with vehicle mix, sunlight, ozone and atmospheric chemistry.
| Route | Why it fits | Design check |
|---|---|---|
| SS2148 / similar 0–20 ppm EC | Fast enough for ventilation and local diesel monitoring. | Confirm alarm/control thresholds and local code. |
| NO2-B43F 4-electrode | Better suited to fixed roadside networks and sub-ppm trends. | Use ozone-rejection filtering and temperature compensation. |
| Multi-pollutant station | Tracks NO₂ together with O₃, CO, PM and meteorological variables. | Co-location and field calibration become system-level requirements. |
Ambient air-quality monitoring
At ppb concentration, zero drift and ozone rejection can matter more than full-scale range.
| Product / route | Range | Architecture | Low-level point |
|---|---|---|---|
| Winsen ZE12A-NO₂ | 0–1 ppm | Conditioned EC module | ≤10 ppb resolution with temperature compensation and DAC / UART. |
| Alphasense NO2-B43F | 0–20 ppm | Filtered 4-electrode EC | PPB roadside / outdoor monitoring with O₃ rejection. |
| Winsen ZEHS04 | Multi-gas | Environmental module | NO₂ measured alongside CO, SO₂ and O₃ in one station architecture. |
Combustion and emissions
High-range NO₂ is only one part of an NOx measurement. Combustion gas often contains much more NO than NO₂, so instrument architecture matters more than a single NO₂ range.
| Product / route | Range class | Engineering point | Official source |
|---|---|---|---|
| Alphasense NO2-AE | 0–200 ppm | Extended-range NO₂ for emissions, stack sampling and industrial upset conditions. | Official ↗ |
| Honeywell 5ND | 0–200 ppm class | 5-Series platform intended for flue-gas / combustion analyzer integration. | 5-Series ↗ |
| NO + NO₂ channels | Application specific | Use separate gas channels when the instrument must report both species or calculate total NOx. | System architecture |
NO₂, NO and NOx are not interchangeable measurements
Nitrogen oxides are produced by combustion, but instruments must distinguish the species they actually measure. A single NO₂ electrochemical sensor reports nitrogen dioxide, not total NOx.
| Term | Meaning | Typical sensor route | Engineering implication |
|---|---|---|---|
| NO | Nitric oxide | Dedicated biased electrochemical NO sensor | Often the dominant NOx species in fresh combustion exhaust. |
| NO₂ | Nitrogen dioxide | Dedicated oxidizing electrochemical NO₂ sensor | This page covers this target gas. |
| NOx | Combined nitrogen oxides, primarily NO + NO₂ in combustion work | Separate NO + NO₂ channels or analyzer / conversion architecture | Do not label a single NO₂ channel as total NOx. |
NO₂ measurement when ozone is present
Ozone and nitrogen dioxide are both strong oxidants. In ambient air, an unfiltered electrochemical oxidant sensor may respond to both, which can create a positive NO₂ bias.
Filtered NO₂ channel
Use a sensor with an internal ozone-rejection filter for a more selective NO₂ measurement.
Example: Alphasense NO2-B43F / NO2-A43F.Oxidant channel
A separate OX sensor responds to O₃ + NO₂ and can be paired with filtered NO₂.
Example: OX-B431 + NO2-B43F.Differential O₃
When both channels are zero- and temperature-corrected, ozone can be derived from the oxidant channel minus the filtered NO₂ channel.
Useful in compact air-quality nodes.Field validation
Roadside ozone and NO₂ vary independently over time. Validate correction using co-location or a reference method.
Especially important at ppb level.Traffic NO₂ sensing needs the right location and gas set
Vehicle exhaust concentration is highly non-uniform. Road geometry, tunnel airflow, diesel fraction, ventilation fans and distance from the traffic lane all change the measured NO₂.
Tunnels and enclosed traffic areas
- Use sensors with response fast enough for the ventilation-control strategy.
- Diesel-heavy traffic can make NO₂ an important control variable.
- CO may still be required; the correct gas set depends on vehicle mix and local code.
- Protect the detector from direct water spray, dust accumulation and exhaust heat.
Roadside air-quality stations
- Use ppb-oriented filtered NO₂ sensing.
- Record temperature/humidity and preferably O₃ alongside NO₂.
- Keep inlet height and distance from the roadway consistent across a network.
- Use field co-location to understand zero drift and site bias.
At low NO₂ levels, zero stability matters more than a wide range
A 20 ppm full-scale sensor can still be useful at ppb concentration, but only if the analog electronics, auxiliary electrode, ozone rejection, temperature correction and enclosure behavior are designed around that low-level signal.
Baseline control
Use the auxiliary electrode or module compensation to correct environmental zero changes.
- Evaluate day/night temperature cycles.
- Check long-term drift, not only laboratory resolution.
Ozone rejection
Use filtered NO₂ or a dual oxidant / NO₂ architecture where ambient O₃ is significant.
- Do not apply a fixed O₃ correction without field validation.
- Filter performance can change with age and exposure.
Station airflow
Outdoor housings need enough air exchange for representative sampling while protecting electronics from rain, dust and condensation.
- Measure enclosure response time.
- Avoid stagnant pockets around the sensor inlet.
A high-range NO₂ cell is only one part of an NOx analyzer
Raw combustion gas can be hot, wet and particulate-laden, and NO / NO₂ ratios change through the sample path. High-range electrochemical cells are useful in portable analyzers, but the gas must reach them under controlled conditions.
Extract sample
Take a representative flue or exhaust sample.
Filter particles
Protect pumps, valves and sensing surfaces.
Control temperature
Bring gas into the sensor's specified operating range.
Manage moisture
Avoid uncontrolled condensation and species changes.
Measure NO + NO₂
Use the channels required by the NOx calculation or method.
Raw NO₂ cell, environmental module or IAQ platform?
Choose a raw / dedicated NO₂ sensor when:
- You need a portable, fixed or ppb NO₂ channel with custom electronics.
- You control the analog front end, bias/polarity and compensation.
- Mechanical size and power must be optimized tightly.
- You need a filtered 4-electrode architecture for outdoor monitoring.
Choose a module when:
- Your controller needs UART, RS485 or conditioned analog output.
- You want temperature compensation handled in the sensor assembly.
- NO₂ is one channel in a broader atmospheric or IAQ system.
- Development speed matters more than minimum BOM cost.
Winsen nitrogen dioxide modules by application
Winsen's current NO₂ offering is module-led: a general toxic-gas module, a low-level atmospheric module, a multi-pollutant outdoor station module and a broad indoor-air-quality platform.
ZE03-NO₂
Current ZE03 manual lists NO₂ 0–20 ppm, 0.1 ppm resolution and T90 ≤30 s. The module provides UART plus analog voltage output with built-in temperature compensation.
ZE12A-NO₂
NO₂ 0–1 ppm, ≤10 ppb resolution, DAC + UART and T90 ≤120 s. Intended for city atmosphere, enterprise environment and fenceline monitoring.
ZEHS04
Diffusion module for CO, SO₂, NO₂ and O₃ with UART or RS485, ≤10 ppb published resolution and optional PM2.5 / PM10 / temperature / humidity expansion.
ZPHS01B
NO₂ 0.1–10 ppm with 0.05 ppm resolution and ≤120 s response, integrated with CO₂, PM2.5, CH₂O, O₃, CO, TVOC, temperature and humidity over UART.
Other nitrogen dioxide sensor product ranges
These manufacturers publish NO₂ sensors for personal safety, roadside monitoring, environmental networks and combustion / emissions analyzers.
Alphasense
Standard, miniature, filtered 4-electrode ppb, smart and extended-range NO₂ sensors.
SENKO
Fast 0–20 ppm electrochemical NO₂ sensor for garage, diesel and portable ambient applications.
Honeywell City Technology
5-Series electrochemical sensors for flue-gas and combustion-analyzer platforms.
Submit an NO₂ sensor
Manufacturers can provide an official product page and current datasheet for inclusion.
NO₂ calibration should verify the complete gas path
Calibration verifies more than cell sensitivity. Enclosure diffusion, filters, tubing, temperature correction and ozone-rejection strategy all affect the finished reading.
Bump test
Confirms that NO₂ reaches the detector and that the measurement / alarm chain responds.
Span calibration
Uses a known NO₂ concentration to establish or adjust response. Follow the instrument's specified flow and stabilization procedure.
Ambient co-location
For ppb air-quality devices, periodic co-location with a reference or higher-grade instrument helps reveal field zero and environmental bias.
Nitrogen dioxide sensor questions
What NO₂ sensor range is common for portable and fixed safety detectors?
A 0–20 ppm electrochemical range is common for worker-safety and general industrial NO2 instruments. Wider ranges are used for combustion or emissions work. Select the range around the alarm region and credible peak concentration, not around the largest number available.
What is the difference between NO₂, NO and NOx?
NO2 is nitrogen dioxide and NO is nitric oxide. NOx is a broader emissions term that usually refers mainly to NO plus NO2. A sensor that measures only NO2 does not by itself report total NOx.
Why is ozone interference important in ambient NO₂ monitoring?
NO2 and ozone are both oxidizing gases and some electrochemical oxidant sensors respond to both. Filtered NO2 sensors can reject ozone, or a paired oxidant/NO2 architecture can be used to calculate separate O3 and NO2 channels.
When should I use a 4-electrode NO₂ sensor?
Use a 4-electrode NO2 sensor when low-level baseline stability matters, especially in roadside, urban-background and fenceline air-quality monitoring. The auxiliary electrode helps correct baseline changes that would be insignificant in a ppm-level safety detector.
Can a 0–20 ppm NO₂ safety sensor be used for flue-gas measurement?
Not for every flue-gas application. Combustion and emissions systems can require much higher range plus temperature control, particulate removal, moisture management and separate NO measurement when total NOx is required.
Is NO₂ useful for parking-garage and tunnel ventilation control?
Yes, particularly where diesel exhaust is significant. CO is also widely used in parking ventilation, so the correct gas set depends on vehicle mix, local code and ventilation strategy. Tunnels and diesel-heavy facilities often benefit from NO2 monitoring.
What is the difference between ZE12A, ZEHS04 and ZPHS01B for NO₂?
ZE12A is a low-range electrochemical environmental module for a single configured gas such as NO2. ZEHS04 combines CO, SO2, NO2 and O3 for atmospheric monitoring. ZPHS01B is a broader indoor-air-quality module combining NO2 with CO2, PM2.5, CH2O, O3, CO, TVOC, temperature and humidity.
How should NO₂ sensors be calibrated?
Use certified NO2 calibration gas and follow the instrument's specified flow and stabilization method. Validate the complete enclosure or sample path, especially where filters or tubing are used, and distinguish a functional bump test from a full span calibration.
Final checks before design freeze
Validate the complete NO₂ instrument against the concentration, gas mixture and environmental conditions expected in service. The sensor cell is only one part of the measurement chain.
- Confirm whether the requirement is NO₂ only or total NOx.
- Match measurement range and T90 to safety, ventilation, ambient or emissions use.
- Check ozone cross-sensitivity in outdoor and roadside applications.
- Use filtered 4-electrode or compensated systems for ppb ambient monitoring.
- Validate enclosure airflow, tubing and filters with target gas.
- For combustion work, control temperature, moisture and particulates before the sensor.
- Confirm the applicable occupational, air-quality or emissions requirements for the final instrument.
Need an NO₂ sensor for an OEM project?
Send the target range, safety / traffic / ambient / emissions application, gas mixture, response requirement, sampling method and output interface. Manufacturers can also submit NO₂ 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.