Carbon Monoxide Sensors
Select a CO sensor by concentration range, application, electrode design, response time and output format. Compare electrochemical elements, conditioned modules, low-level environmental sensors and high-range combustion options.
CO sensor range by measurement task
Full-scale range is the first filter. A residential alarm, worker-safety instrument, low-level air monitor and combustion analyzer do not use the same design priorities.
500–1,000 ppm class
Prioritize long operating life, low sensing power, stable baseline and compatibility with alarm standards.
- Raw long-life electrochemical element
- Pre-calibrated / conditioned module
1,000–2,000 ppm class
Fast T90, robust environmental performance and predictable interference behavior are more important than maximum range alone.
- 3-electrode electrochemical
- Compact / standard industrial packages
Low ppm / ppb-oriented
Use a high-output 4-electrode sensor with low-noise electronics and baseline compensation.
- Auxiliary electrode
- Low zero drift
5,000–10,000 ppm class
High-range cells avoid saturating conventional alarm sensors. Combustion gases also increase the importance of filters and sample handling.
- Extended-range electrochemical
- Check H₂ and other combustion-gas response
UART / PWM / analog
Choose a conditioned module when the controller needs concentration data rather than a raw nA/ppm signal.
- Shorter analog design cycle
- Calibration / diagnostics may be integrated
MOS / MEMS-MOX
Useful in embedded designs where heater power, warm-up and broader cross-gas response are acceptable and can be handled in the product design.
- Heater control required
- Not a direct replacement for selective EC safety sensing
Electrochemical CO sensing: 2, 3 and 4 electrodes
Dedicated CO safety sensors are commonly electrochemical. The electrode count changes the way the cell is controlled and how well the system can manage baseline error.
2-electrode
A working/counter pair generates the CO-dependent current. This architecture is used in several long-life residential CO sensors.
Examples: Figaro TGS5141/TGS5042, Honeywell ECO-SURE family.3-electrode
A reference electrode controls working-electrode potential and is common in portable and fixed industrial toxic-gas instruments.
Examples: Honeywell 4CM, Alphasense H-Series, Winsen ME4-CO.4-electrode
An auxiliary electrode provides a second baseline signal that can be used to compensate zero changes in low-level measurement.
Examples: Alphasense CO-B4, Winsen ME4-CO-E4.MOS / MEMS-MOX
A heated metal oxide changes resistance in CO. It is compact and cost-effective but has different selectivity, warm-up and power requirements.
Examples: Winsen MQ-7B and GM-702B.CO sensors and modules for OEM design
Shortlist by the engineering requirement first: long-life alarm, portable safety, low-hydrogen response, low-level environmental monitoring, high-range combustion or conditioned output. The products below represent different design routes rather than a single manufacturer lineup.
| OEM need | Manufacturer | Model | Type | Published range | Key engineering point | Official source |
|---|---|---|---|---|---|---|
| Long-life residential alarm | Winsen | MEs-CO | Fuel-cell electrochemical | 0–1,000 ppm max 2,000 ppm |
10-year published life, T90 <30 s, UL and EN50291-1 noted on the current product page. | Official ↗ |
| Compact residential / fire alarm | Figaro | TGS5141-P00 | 2-electrode electrochemical | 0–5,000 ppm | Ultra-compact, battery operable, 0 mW sensing element; T90 within 60 s on current technical information. | Official ↗ |
| Portable life-safety detector | Honeywell City Technology | 4CM | 3-electrode electrochemical | 0–2,000 ppm | T90 ≤10 s up to 500 ppm at 20°C; acid-gas filter; standard 4-Series format for portable detectors. | Official ↗ |
| Portable safety in H₂-rich areas | Alphasense | CO-H4X | Filtered H-Series electrochemical | 0–1,000 ppm | Low hydrogen cross-sensitivity, compact H-Series package, T90 <25 s. | Official ↗ |
| Compact digital OEM | Winsen | SME100-CO SMX100 Series |
Intelligent electrochemical | 0.5–1,000 ppm | UART output, 1 ppm resolution, T90 <30 s, 5-year expected life and low-profile package. | Official ↗ |
| Conditioned analog module | Figaro | CMM5042 | Pre-calibrated electrochemical module | 0–800 ppm | 0–2 V analog output, ≤30 s warm-up and T90 within 60 s; based on TGS5042. | Official ↗ |
| Low-level environmental CO | Winsen | ME4-CO-E4 | 4-electrode electrochemical | 0–1,000 ppm max 2,000 ppm |
Auxiliary electrode for zero compensation; <10 ppb published resolution. | Official ↗ |
| Low-level environmental CO | Alphasense | CO-B4 | 4-electrode B-Series | 0–1,000 ppm | High-output, low-noise 4-electrode architecture for ppb-level environmental and perimeter monitoring. | Official ↗ |
| High-range generator / industrial CO | Winsen | ME2-CO-Φ14×5 | Compact electrochemical | 0–5,000 ppm max 10,000 ppm |
T90 <30 s; intended for generators, vehicles and high-range commercial / industrial CO measurement. | Official ↗ |
| Combustion / stack measurement | Alphasense | CO-CE | C-Series electrochemical | 0–10,000 ppm | High-range stack-gas design with extra carbon filtering; positioned for combustion analyzers and EN 50379 applications. | Official ↗ |
Published values are manufacturer component specifications. Confirm the latest datasheet, cross-sensitivity data and finished-product requirements before design freeze.
Compare CO sensors by application
Compare products within the same measurement task. A long-life alarm sensor, a ppb environmental sensor and a 10,000 ppm combustion sensor should be evaluated against different engineering criteria.
Residential / long-life CO alarms
Low sensing power, long operating life and stable response over temperature/humidity are the main design priorities.
| Manufacturer | Model | Range | Published point to compare | Official source |
|---|---|---|---|---|
| Winsen | MEs-CO | 0–1,000 ppm | 10-year published life; UL and EN50291-1 noted on product page | Official ↗ |
| Figaro | TGS5141-P00 | 0–5,000 ppm | Ultra-compact 2-electrode electrochemical; 0 mW sensing element; residential/fire applications | Official ↗ |
Portable & fixed industrial safety
Response time, package, environmental range and interference behavior carry more weight than maximum ppm alone.
| Manufacturer | Model | Range | T90 | Engineering point | Official source |
|---|---|---|---|---|---|
| Winsen | ME4-CO | 0–1,000 ppm | ≤25 s | Standard 32 mm industrial cell; 2-year published life in air | Official ↗ |
| Alphasense | CO-H4X | 0–1,000 ppm | <25 s | Compact H-Series with chemical filter to reduce H₂ cross-sensitivity | Official ↗ |
| Honeywell City Technology | 4CM | 0–2,000 ppm | ≤10 s up to 500 ppm at 20°C | 3-electrode 4-Series life-safety cell; acid-gas filter | Datasheet ↗ |
Low-level / environmental CO
At low concentration, baseline compensation and signal-to-noise ratio matter more than full-scale range.
| Manufacturer | Model | Architecture | Range | Low-level point | Official source |
|---|---|---|---|---|---|
| Winsen | ME4-CO-E4 | 4-electrode | 0–1,000 ppm | <10 ppb published resolution; auxiliary electrode for zero compensation | Official ↗ |
| Alphasense | CO-B4 | 4-electrode B-Series | 0–1,000 ppm | High output / low noise with 4-electrode baseline compensation capability | Official ↗ |
High-range / combustion CO
Use an extended-range cell where CO can rise into several thousand ppm. Combustion sampling also requires attention to H₂ and other flue-gas interferents.
| Manufacturer | Model | Range | T90 | Engineering point | Official source |
|---|---|---|---|---|---|
| Winsen | ME2-CO-Φ14×5 | 0–5,000 ppm; max 10,000 | <30 s | Compact high-range cell for generators, vehicles and industrial CO | Official ↗ |
| Alphasense | CO-CE | 0–10,000 ppm | <75 s | C-Series combustion / stack sensor with additional carbon filtering; EN 50379 positioning | Official ↗ |
| Figaro | TGS5042 | 0–10,000 ppm | Application dependent | Battery-operable 2-electrode sensor; 10-year expected life on current Figaro feature page | Official ↗ |
Conditioned / OEM modules
Module comparison should focus on interface, range, warm-up and integration burden.
| Manufacturer | Model | Range | Output | Engineering point | Official source |
|---|---|---|---|---|---|
| Winsen | SME100-CO | 0.5–1,000 ppm | UART | Low-profile intelligent sensor with built-in diagnostics/adaptive functions; 5-year expected life | Official ↗ |
| Winsen | ZE730-CO | 0–1,000 ppm | UART / PWM | General-purpose conditioned module, -20 to 80°C published working range | Official ↗ |
| Figaro | CMM5042 | 0–800 ppm | 0–2 V analog | Pre-calibrated TGS5042-based module; ≤30 s warm-up, T90 within 60 s | Official ↗ |
CO sensor priorities by application
Residential CO alarms
Design for years of unattended service. Long life, low sensing power, baseline stability and compliance testing matter more than the widest possible range.
- Long-life electrochemical element or module
- Verify end-of-life / fault strategy
- Component recognition does not certify the finished alarm
Portable gas detectors
Fast T90, small package and predictable cross-sensitivity matter. A low-H₂ variant may be required in hydrogen or fuel-cell environments.
- 3-electrode compact electrochemical
- Low H₂ cross-sensitivity when needed
- Bump-test gas path and alarm response
Fixed industrial CO
Check long-term environment, enclosure diffusion, temperature/humidity and service interval. The cell is only one part of detector response.
- Standard industrial format
- Remote or diffusion sampling
- Calibration access
Parking garages
CO sensing is used for ventilation control, but sensor range and placement must match local code, traffic pattern and ventilation design.
- Low-to-mid ppm control range
- Site-specific spacing and airflow
- Maintenance/calibration plan
Environmental monitoring
Low signal level changes the electronics problem. Baseline compensation, ppb resolution, temperature correction and co-location/reference checks become central.
- 4-electrode CO cell
- Low-noise AFE
- Environmental compensation
Combustion / flue gas
Expect thousands of ppm and a mixed gas background. Choose high-range CO, minimize sample delay and review H₂/combustion-gas interference.
- 5,000–10,000 ppm class
- Sample conditioning
- Combustion-specific filter design
Raw CO sensor or conditioned module?
Choose a raw electrochemical element when:
- Your team will design the transimpedance / potentiostat circuit.
- High-volume BOM cost matters.
- You need full control of digital filtering and calibration.
- The mechanical gas path is tightly integrated with your enclosure.
- You need a standard 20 mm, 32 mm or miniature cell format.
Choose a module when:
- Your MCU needs UART, PWM or conditioned analog output.
- Engineering time is more important than the lowest component cost.
- You want integrated amplification / ADC / compensation.
- The module’s mechanical size fits the final product.
- Field replacement is easier with a defined digital interface.
CO sensors in hydrogen-rich environments
Standard CO electrochemical cells can respond to hydrogen. The error can be unacceptable around hydrogen production, fuel cells, battery systems, hydrogen blending or combustion processes.
Check the exact H₂ response
Do not assume that every CO sensor from the same manufacturer has the same hydrogen response. Filters and electrode chemistry differ by model.
Use a low-H₂ variant when required
Alphasense CO-H4X is specifically published with a chemical filter to reduce H₂ cross-sensitivity. Other manufacturers also offer filtered or compensated CO variants.
Validate the real gas mixture
Cross-sensitivity tables are screening data. Test the complete detector with expected H₂ concentration, CO concentration, temperature and humidity.
Response time, resolution and accuracy are different specifications
T90 response time
Time for the sensor output to reach 90% of its final response after a gas step under the manufacturer’s test conditions.
- Finished detector response also includes enclosure diffusion, tubing/pump delay, filters and firmware averaging.
Resolution
The smallest concentration change that can be resolved by the sensor/electronics combination.
- 1 ppm resolution does not mean ±1 ppm measurement accuracy.
- PPB-oriented sensors still need low-noise electronics and baseline compensation.
Accuracy
A system-level result that includes calibration, sensitivity tolerance, zero error, temperature/humidity effects, electronics and gas-delivery uncertainty.
- For regulated instruments, use the accuracy requirements of the finished-product standard, not only the sensor datasheet.
Published sensor life is not the service interval
CO electrochemical sensors can be published with operating lives from roughly two years to ten years or more, depending on the construction and intended application. Field life is still affected by storage, temperature, humidity, target-gas load and interfering gases.
Sensor life
Use the manufacturer’s life figure as a design input. Define end-of-life behavior and replacement logic for the finished instrument.
Bump test
A bump test confirms that gas reaches the sensor and that the instrument responds and alarms. It is a functional check, not a full accuracy calibration.
Calibration
Calibration applies a known CO concentration to establish or adjust the measurement. Follow the instrument manufacturer and the applicable maintenance procedure.
Additional sensor formats and manufacturer ranges
The shortlist above covers the main engineering routes. Additional products are useful when the design needs a different footprint, output method, lifetime, range or sensing principle.
More raw CO elements
Additional Winsen electrochemical formats cover compact portable sensors, standard industrial cells and long-life alarm designs.
Conditioned and digital CO
Use a module when the controller needs UART, PWM or conditioned analog output instead of a raw electrochemical current.
Additional CO sensor manufacturers
Alphasense
Portable, fixed, low-H₂, 4-electrode, dual-gas and high-range CO sensors.
Figaro Engineering
Long-life electrochemical CO sensors and pre-calibrated modules.
Honeywell City Technology
4-Series and residential CO sensing platforms for life-safety equipment.
Nemoto
Electrochemical CO sensors for residential, industrial and specialist applications.
SGX Sensortech
CO sensor formats available through the official sensor selector.
Submit a CO sensor
Manufacturers can provide an official product page and current datasheet for inclusion.
Carbon monoxide sensor questions
What CO sensor range should I use for a residential alarm?
A residential CO alarm normally does not need the same full scale as a combustion analyzer. Evaluate long-life electrochemical sensors in the hundreds to low-thousands ppm range, then verify the finished alarm against the applicable market standard. Wider range is not a substitute for stable low-level response and long-term reliability.
When is a 4-electrode CO sensor useful?
A fourth, auxiliary electrode is useful when the design needs better compensation for baseline changes. This is especially relevant in low-level environmental monitoring, where the useful signal can be small compared with temperature-related zero movement and electronic noise.
Why do some CO sensors respond to hydrogen?
Hydrogen can generate a response on some CO electrochemical chemistries. If the detector is used around hydrogen production, fuel cells, battery systems or hydrogen-rich combustion gas, check the exact H2 cross-sensitivity or use a filtered / low-H2 variant.
Is 1 ppm resolution the same as ±1 ppm accuracy?
No. Resolution is the smallest displayed or quantized change. Accuracy also includes sensor sensitivity tolerance, zero error, temperature/humidity effects, calibration gas uncertainty, analog electronics and signal processing.
Should I choose a raw CO sensor or a module?
Choose a raw element when your team will design the analog front end, compensation and calibration. Choose a module when UART, PWM or conditioned analog output is more useful than controlling the electrochemical signal chain directly.
What is the difference between electrochemical, MOS and MEMS CO sensors?
Electrochemical sensors generate a small current from the CO reaction and are widely used for dedicated quantitative CO safety measurement. MOS and MEMS-MOX sensors use a heated metal oxide whose resistance changes with gas exposure; they need heater control and normally have broader cross-gas response.
Can one CO sensor cover both personal safety and flue-gas measurement?
Sometimes a wide-range sensor can survive both concentration regions, but that does not make it optimal for both. Personal safety favors fast low-level response and compact integration; flue-gas work can require thousands of ppm, combustion-gas filtering and different sampling hardware.
How often should a CO sensor be calibrated?
Follow the finished instrument manufacturer and the site maintenance procedure. Calibration frequency depends on the sensor, application, exposure history and regulatory requirements. A bump test checks response and gas path; calibration establishes or adjusts measurement accuracy.
Need a CO sensor for an OEM project?
Send the target range, application, operating environment, preferred output and product format. Manufacturers can also submit CO sensor models with an official product page and datasheet.
Specifications and product availability can change. Confirm the latest manufacturer datasheet before engineering, compliance or purchasing decisions.