Air quality sensor is use to measure the concentration of greenhouse gas in the air. Voltage Comparator is a device which compares two voltages which are reference voltage and input voltage. Potentiometer is a three terminal variable resistor. VCC pin is used to power the sensor. (5V DC supply). Ground pin is used to connect the sensor to the ground. D0 (Digital Output) pin is used to get the digital output from the sensor, by setting the proper threshold by potentiometer. A0 (Analog Output) pin is used for 0 to 5V analog voltage, which is based on the intensity of the gas.