| Air Quality MQ135 sensor by BARRAGAN <http://barraganstudio.com> Reads values from an air quality sensor connected to the analog input pin 0. The value read from the sensor is proportional to the air quality measured by the sensor. The value read is printed through the serial to be monitored in the console. Created 5 April 2009 |

    // Air Quality MQ135 sensor
    // by BARRAGAN <http://barraganstudio.com>

    int val;

    void setup()
    {
      Serial.begin(9600);           // sets the serial port to 9600
    }

    void loop()
    {
      val = analogRead(0);          // read analog input pin 0
      Serial.print(val, DEC);       // prints the value read
      Serial.print(" ");		// prints a space between the numbers
      delay(100);                   // wait 100ms for next reading
    }