The GS302M-DL-AL carbon dioxide sensor module based on NDIR principle, is widely used to detect the carbon dioxide in the air. It outputs the carbon dioxide concentration through UART or PWM interface. It has a built-in thermistor for temperature compensation. It adopts a single-light source and a dual-channel detector to realize dual-path reference compensation in space. It has been calibrated in Multi IR’s humidity and temperature controlled facility, so it can be used directly in the testing instruments and moni- toring equipment.