This is the first CO2 sensor in the Arduino market. The output voltage of the module falls as the concentration of the CO2 increases. The potentiometer onboard is designed to set the threshold of voltage. As long as the CO2 concentration is high enough (the voltage is lower than the threshold), A digital signal (ON/OFF) will be released.
It has MG-811 sensor module which is highly sensitive to CO2 and less sensitive to alcohol and CO, low humidity & temperature dependency.
Onboard heating circuit brings the best temperature for the sensor to function. Internal power boosting to 6V for heating sensor best performance.
This sensor has an onboard conditioning circuit for amplifying output signal.
To ease the difficulty of using this CO2 sensor, a Gravity Interface is adapted to allow plug&play. The Arduino IO expansion shield is the best match for this CO2 senor connecting to your Arduino microcontroller.
This is an electrochemical Arduino-based CO2 sensor, it is suitable for qualitative analysis. There are other Infrared CO2 sensors, which could make a quantitative analysis.