The LCN-CO2 is a CO2 sensor for indoor use. Can be used for all LCN modules from version 120C05. It detects CO2 concentrations of 1-5000 ppm. The robust and compact sensor works with an infrared-based spectroscopic measuring method to measure the CO2 content in the air. It reacts to even the smallest changes in the air composition. The LCN-CO2 can be combined with any I-connection peripheral on the I-connection of all intelligent LCN modules (-UPP, -UPS, -UP24, -SH, -SHS, -HU, -LD). The LCN-CO2 can affect the controllers and the switching thresholds. Measured values can be exchanged between LCN modules and used for calculations. The LCN-CO2 measures the carbon dioxide (CO2) content of the air inside buildings. This enables energy-efficient control of the ventilation and air conditioning system and thus allows the supply of fresh air as needed. The LCN-CO2 thus actively contributes to healthy indoor air quality.