   concentrations of CO, NO2, VOC (derived) and CO2 (derived)
 
   Currently untested: TSL2561 light sensor code
-  Currently untested: MAX4466 mic + amp code
+  Currently untested: ADMP401 mic code
   
   Designed at CRT Labs (July 2016)
   https://github.com/NationalAssociationOfRealtors/SensorBoard
   
-  Modified: 6 September 2016
+  Modified: 8 September 2016
   by Akram Ali
  */
 

  //Serial.println(Rs);
  //Serial.println(R0);
  //Serial.println(ratio);
  Serial.println(concentration);
  return concentration;
}

float readNO2()

  
  Serial.println("---------------------");
  
  // ADMP401 mic for sound level
  Serial.print("Sound Level: ");
  Serial.print(analogRead(A0));  // read sound levels
  Serial.println();


  // TSL2561 light sensor
