Gravity: Analog CO2 Gas Sensor (MG-811 Sensor)

Great and powerful sensor for everyone that wants to know the exact concentration of CO2(Carbon Dioxide) in the air.
This is the first CO2 sensor compatible with Arduino. 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.
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.