In September 2024, updated information was released about the Infineon photo-acoustic sensor and outdoor performance of photo-acoustic sensors. When it comes to low-cost CO2 sensors, there are three methods to measure CO2: eCO2 through TVOC sensors, NDIR sensors, and photo-acoustic sensors. TVOC sensors are not recommended for CO2 estimation due to their unreliability. NDIR and photo-acoustic sensors measure CO2 directly based on gas absorption principles. Photo-acoustic sensors are smaller and can detect CO2 levels without line-of-sight. Tests show that NDIR sensors are more accurate and reliable compared to photo-acoustic sensors, especially outdoors due to varying environmental conditions. It is advised to use SenseAir S8 for accurate indoor CO2 monitoring.
https://www.airgradient.com/blog/co2-sensors-photo-acoustic-vs-ndir-updated/