A carbon dioxide sensor or CO2 sensor is an instrument for the measurement of carbon dioxide gas. The most common principles for CO2 sensors are infrared gas sensors (NDIR) and chemical gas sensors. Measuring carbon dioxide is important in monitoring indoor air quality, the function of the lungs in the form of a capnograph device, and many industrial processes.
Chemical CO2 gas sensors with sensitive layers based on polymer- or heteropolysiloxane have the principal advantage of a very low energy consumption, and can be reduced in size to fit into microelectronic-based systems. On the downside, short- and long term drift effects as well as a rather low overall lifetime are major obstacles when compared with the NDIR measurement principle. Most CO??? 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 long term stability of the sensor.
Indoor air quality
Cellar and gas stores
For HVAC applications, CO2 sensors can be used to monitor the quality of air and the tailored need for fresh air, respectively. Measuring CO2 levels indirectly determines how many people are in a room, and ventilation can be adjusted accordingly. See demand controlled ventilation (DCV).
In applications where direct temperature measurement is not applicable, NDIR sensors can be used. The sensors absorb ambient infrared radiation (IR) given off by a heated surface