What are CO2 Sensors?

What are CO₂ Sensors?

CO₂ (carbon dioxide) sensors measure CO₂ to monitor indoor air quality, often as part of an HVAC system. They are also found in medical equipment and various industrial applications.

The amount of carbon dioxide in the air is an indicator of the performance quality of the HVAC system. CO₂ sensors help ensure an adequate fresh air supply. CO₂ increases as occupancy increases. CO₂ sensors, along with other HVAC sensors, help meet building safety guidelines by adjusting the intake of fresh outside air to dilute the amount of CO₂ present as well as dust, VOCs (volatile organic compounds), and other contaminants. This allows the ventilation system to maintain comfort and safety and prevents over-ventilation of low-occupancy areas.

Types of CO₂ sensors

NDIR sensors

CO₂ meters for air quality typically use NDIR (non-dispersive infrared) sensors. These are spectroscopic sensors that detect CO₂ in a gaseous environment and are the most common and accurate means of measuring CO₂.

NDIR combines an infrared source, a light tube, an interference (wavelength) filter, and an infrared detector. Gas is pumped or diffused into the light tube and electronics measure the light absorption. The amount of absorbed light is directly proportional to the concentration of CO₂ in the air. The sensors ideally have sensitivities of 20-50 PPM. These devices ensure compliance with building standards that focus on the wellbeing of building occupants.

Other uses of NDIR CO₂ sensors include measuring dissolved CO₂ in carbonated beverages, pharmaceutical fermentation, and CO₂ sequestration applications.

Amphenol Advanced Sensors’ Telaire brand T3022 series of NDIR CO2 sensors from Heilind Electronics.

Photoacoustic sensors

CO₂ concentration is measured by subjecting a sample to pulses of electromagnetic energy tuned to the absorption wavelength of CO₂. The CO₂ molecules in the sample absorb and generate pressure waves, which are detected with an acoustic detector and converted to a usable CO₂ reading with a computer or microprocessor.

Chemical sensors

Chemical CO₂ gas sensors have very low energy consumption and can fit into microelectronic-based systems. However, short and long term drift effects and short overall lifetime make them less effective than NDIR. Most CO₂ sensors are fully calibrated prior to shipping from the factory. Over time, the zero point of the sensor needs to be calibrated to maintain the sensor’s stability.

Other sensor types are electromechanical and metal oxide semiconductor (MOS) sensors.

Markets and Applications 

Industrial, Medical

Monitoring air quality, HVAC systems.

For patients under anesthesia or in intensive care, they are used in capnography, which measures the carbon pressure in the lungs

Suppliers 

Heilind Electronics (Amphenol Advanced Sensors)

Related products

Temperature sensors

Humidity sensors

Pressure sensors

Position sensors

Flow sensors

Vibration sensors

Gas sensors

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