MQ135 sensor program Arduino

#include <MQ135.h>
MQ135 gasSensor = MQ135(5);
int maxppm = 1000; //Ppm max value allowed by “law”
int comfortval = 600; //Ppm comfort val
int fanOutput = 10; //Digital pin 10 with analog write capabilities
int warningLED = 7; //Digital led pin
int analogSensorPin = 5;
int sensorValue;
float ppm; //CO2 levels in PPM
float rzero; //Only required for calibration

void setup() {
  //delay(120000); //2min sensor initialize
  Serial.begin(9600); //Start console
  pinMode(fanOutput, OUTPUT); //Fan output
  pinMode(warningLED, OUTPUT); //Fan output
  rzero = gasSensor.getRZero(); //Only required for calibration
  //Print RZero nicely
  Serial.print("===== RZero: ");
  Serial.print(rzero);
  Serial.print(" =====");
  Serial.println("");
}

void loop() {
  digitalWrite(warningLED, 0); //Set led voltage to zero to make sure there’s no misunderstandings
  sensorValue = analogRead(analogSensorPin); //Analog sensor input
  ppm = gasSensor.getPPM(); //Grap current ppm val for CO2 using the lib
  Serial.println(ppm); //Print ppm val

  if (ppm > maxppm) //WARNING: Limit reached! Set red LED.
  {
    digitalWrite(warningLED, 1);
  }

  if (ppm > comfortval) //Reaching high levels of CO2, set full power to fan.
  {
    analogWrite(fanOutput, 0);
  }

  else //Half power (normal speed)
  {
    analogWrite(fanOutput, 127.5);
  }
  delay(1000); //Only check every second.
}