DFRobotSEN0159Sensor Development Boards and Kits

The SEN0159 by DFRobot is the first carbon dioxide sensor on the OSHW market. This sensor's operating principle is straightforward: as environmental CO2 concentration increases, the output voltage of the sensor decreases. 
The SEN0159 emits a signal whenever the output voltage falls bellows a certain threshold (CO2 is above a certain threshold). The SEN0159 uses a MG-811 sensor that is highly sensitive to CO2 ― though less sensitive to CO and alcohol ― with a low dependency on humidity and temperature to ensure accurate readings. An onboard heating circuit keeps the unit in the proper temperature for optimal functioning.