Carbon dioxide (CO₂) is considered one of the most important agents in the Earth's climate system. It is not only responsible for the greenhouse effect that promotes global warming but also highly toxic in higher concentrations. It is on the other hand a necessary resource for the sustaining of life by producing oxygen through photosynthesis – thus forming both foundation and threat to all life.

Due to this critical role of CO₂, it is generally in the human interest to monitor the environment for its concentration, in order to draw conclusions about CO₂-induced effects and mechanisms. Miniaturized photoacoustic spectroscopy (PAS) provides a way to measure CO₂ in a cheap and robust way with small form factors.

PAS sensors comprise a measuring chamber, an (infrared) emitter and a microphone. The underlying principle is the so-called photoacoustic effect: light of a certain wavelength excites the gas molecules to be detected, which in turn emit this excitation as heat to surrounding molecules. This emitted heat leads to a pressure surge in a closed measuring chamber, which a microphone can measure (See Figure 1)