© Fraunhofer EMFT / Bernd Müller

USB stick with sensor device to measure humidity and CO2

That is why sensor-based systems monitoring room air quality and providing regular boosts of fresh air are becoming more and more common. CO2 sensors currently available on the market generally use an optical measuring principle. They have some drawbacks, though: they are big, expensive, and also use a relatively high amount of energy – which makes them only to a limited extent suitable for the growing smart home market.

 A research team at Fraunhofer EMFT took a different approach and has developed a CO2 sensor that works based on an impedimetric measuring principle. This means that a gas-dependent change in the capacity of a sensor layer forms the basis of the sensor signal. The Munichbased scientists have now developed a new type of hybrid sensor layer comprising a combination of organic and anorganic material. It is showing very promising results so far: the sensor can detect CO2 concentrations of only 440 ppm and boasts low response and regeneration times of less than 2.5 min. In long-term tests, it operates reliably and stably for many weeks at a time – without the occurrence of signal drift, a relatively common problem with chemical sensors.


The electronic CO2 “nose” is suitable not only for monitoring air quality: the scientists are looking at carbon monoxide (CO) and sulfur dioxide (SO2) detection as possible future applications.