Carbon Monoxide (CO) Gas Sensor

Carbon monoxide is an invisible, odourless product of incomplete combustion — produced wherever fossil fuels burn without sufficient oxygen. Vehicle engines, construction generators, industrial boilers, and tunnels are all sources of CO that require continuous monitoring to protect public health and worker safety. The Sensorbee CO Sensor is an electrochemical gas sensor module that detects carbon monoxide at concentrations as low as 10 parts per billion, with a response time under 30 seconds — the fastest in the Sensorbee gas sensor range. This 25-gram plug-in module integrates with the Air Pro 2 and Air Lite monitoring platforms for real-time CO detection in traffic, tunnel, industrial, and construction monitoring applications.

How It Works

The CO sensor uses electrochemical detection — carbon monoxide molecules diffuse through a gas-permeable membrane and oxidise at a working electrode, generating an electrical current proportional to the CO concentration. This proven sensing mechanism delivers reliable, continuous measurement at ambient concentration levels without the infrared optical systems required by reference-grade CO analysers.

What distinguishes the CO sensor from other modules in the Sensorbee gas sensor range is its response speed. At under 30 seconds, the CO sensor responds roughly twice as fast as the NO2, SO2, and O3 modules. This speed matters in safety-critical applications like tunnel monitoring and confined space ventilation, where rapid detection of rising CO concentrations can trigger immediate protective actions.

The module measures 55 × 40 × 30 mm, weighs 25 grams, and operates across -30 to +50°C in a polyamide enclosure. Factory calibration means the sensor is ready for deployment immediately upon insertion into the base station.

Why CO Monitoring Matters

Carbon monoxide binds to haemoglobin in the blood far more readily than oxygen, reducing the blood's oxygen-carrying capacity. Even moderate exposure can cause headaches, dizziness, and impaired cognitive function — with prolonged high-level exposure being potentially fatal. Key CO monitoring applications include:

• Road traffic assessment — vehicles produce CO through incomplete combustion, with concentrations highest at congested intersections, within street canyons, and near parking structures
• Tunnel and underground spaces — enclosed road tunnels and underground car parks accumulate CO from vehicle exhaust, requiring continuous monitoring to manage ventilation systems
• Construction sites — diesel generators, concrete saws, and other combustion equipment produce CO in areas where workers may be exposed, particularly in partially enclosed or below-grade work areas
• Industrial safety — furnaces, boilers, and process heaters generate CO that must be monitored at both the source and the facility perimeter

The 10 ppb limit of detection and fast response time make the Sensorbee CO sensor suitable for both ambient air quality monitoring and safety-oriented applications where rapid detection is essential.

Measurement Performance

The CO sensor provides 10 ppb resolution across a 0–7,000 ppb measurement range, with ±80 ppb typical accuracy and 20 ppb repeatability. The measurement range is calibrated for ambient monitoring scenarios — urban background CO levels typically range from 200–1,000 ppb, while near-road and enclosed environments may reach several thousand ppb during peak periods.

The 1,000 ppm guarantee range provides significant headroom above the measurement range, protecting the sensor from damage during extreme exposure events. This is particularly important in tunnel and confined space applications where momentary high concentrations can occur during ventilation failures or traffic incidents.

Fast Response for Safety Applications

The sub-30-second response time is the CO sensor's standout characteristic. In tunnel monitoring systems, where ventilation fans are activated based on pollutant concentrations, rapid detection means faster response — reducing the window during which workers or the public are exposed to elevated CO levels.

This fast response also benefits mobile monitoring applications where the sensor moves through different concentration zones. When mounted on a mobile platform surveying traffic routes or construction sites, the CO sensor tracks concentration changes in near real-time, providing a spatial profile of CO levels along the survey route.

Integration With Sensorbee Platforms

The CO sensor plugs directly into the Air Pro 2 or Air Lite base station with no configuration required. The base station handles all signal processing, data logging, and transmission.

For traffic and urban monitoring, the CO sensor is typically deployed alongside NO2 and particulate matter sensors to provide a comprehensive combustion emissions profile. In industrial settings, combining CO with SO2 and NO2 sensors creates a multi-parameter emissions monitoring capability from a single station.

The Sensorbee Cloud platform receives real-time CO data via the base station's cellular connection. Alert thresholds can be configured to trigger immediate notifications when CO concentrations exceed safety or air quality limits — critical for tunnel management and construction site safety applications.

Deployment and Maintenance

Insert the CO sensor module into the Air Pro 2 or Air Lite base station. The platform detects the sensor automatically and begins data acquisition. No wiring, calibration, or configuration is needed at the deployment site.

The sensor operates continuously for over one year before replacement. The plug-and-play replacement process takes under two minutes — remove the old module and insert a new factory-calibrated unit. For safety-critical applications, scheduled replacement before the end of operational life ensures uninterrupted monitoring coverage.

The wider operating temperature range (-30 to +50°C) and humidity tolerance (15–90% RH) compared to some other gas modules makes the CO sensor suitable for deployment in both outdoor ambient monitoring and the challenging environments found inside road tunnels and industrial facilities.

Applications

• Traffic and roadside monitoring — measure CO at congested intersections, street canyons, and near-road locations to assess vehicle emission impacts on air quality
• Tunnel ventilation management — continuous CO monitoring to control mechanical ventilation systems in road tunnels, maintaining safe air quality for drivers and maintenance workers
• Construction site safety — monitor CO from diesel generators, vehicles, and combustion equipment in partially enclosed or below-grade work areas
• Underground car park monitoring — real-time CO measurement to manage ventilation and protect public health in enclosed parking facilities
• Industrial safety monitoring — perimeter and near-source CO measurement at facilities operating combustion equipment, boilers, and furnaces
• Environmental baseline studies — CO measurement for air quality assessments supporting planning applications and environmental impact evaluations

Frequently Asked Questions

Why is the response time faster than other Sensorbee gas sensors?

The electrochemical cell design for CO is optimised for rapid diffusion and reaction kinetics. Carbon monoxide's molecular properties allow faster transport through the sensor membrane than larger molecules like SO2 or O3, resulting in a sub-30-second response time compared to the 45–80 second response times of other gas modules.

Can this sensor be used for indoor air quality?

Yes — CO is a relevant indoor pollutant where gas appliances, heating systems, or vehicle exhaust infiltration may be present. The 10 ppb limit of detection provides the sensitivity needed for indoor monitoring, where concentrations are typically lower than outdoor traffic environments.

How does this work with tunnel ventilation systems?

The CO sensor feeds real-time concentration data to the Sensorbee Cloud, which can be integrated with building management or SCADA systems via API. When CO levels exceed configured thresholds, automated alerts trigger ventilation system responses. The fast response time minimises the delay between a concentration increase and the ventilation response.

What is the cross-sensitivity to hydrogen?

Electrochemical CO sensors have a known cross-sensitivity to hydrogen gas. In most ambient air quality applications, hydrogen concentrations are negligible and do not affect CO measurement. For deployment in environments where hydrogen may be present (e.g., near hydrogen production or storage), consult the sensor datasheet for correction factors.

Can I measure CO and CO2 simultaneously?

Yes — the CO sensor (SB4262) and CO2 sensor (SB4212) are separate modules that can be deployed on the same Air Pro 2 base station. They use different sensing technologies (electrochemical for CO, photoacoustic for CO2) and measure independently.