A carbon dioxide transmitter measures CO₂ concentration using infrared (NDIR) or electrochemical sensing technology. In NDIR sensors, an infrared light beam passes through the air sample, and the amount of absorbed light correlates to CO₂ concentration. The sensing signal is then converted by the transmitter’s electronics into a standardized output, such as 4–20 mA or digital communication. This output is sent to building management or control systems for ventilation control, air quality
