const int AOUTpin=0; //the AOUT pin of the methane sensor goes into analog pin A0 of the arduino
const int DOUTpin=8; //the DOUT pin of the methane sensor goes into digital pin D8 of the arduino
const int ledPin=13; //the anode of the LED connects to digital pin D13 of the arduino

int limit;
int value;

void setup()
{
Serial.begin(9600); //sets the baud rate
pinMode(DOUTpin, INPUT);
pinMode(ledPin, OUTPUT);
}

void loop()
{

value= analogRead(AOUTpin); //reads the analaog value from the methane sensor's AOUT pin
limit= digitalRead(DOUTpin); //reads the digital value from the methane sensor's DOUT pin

Serial.print("CO value: ");
Serial.println(value); //prints the methane value
Serial.print("Limit: ");
Serial.print(limit); //prints the limit reached as either LOW or HIGH (above or below)
delay(1000);

if (limit == HIGH)
{
 digitalWrite(ledPin, HIGH); //if limit has been reached, LED turns ON
}
else
{
 digitalWrite(ledPin, LOW); //if limit not reached, LED remains OFF
}

}