I need help to solve my seketch problem

I am using Mq gas sensor for my project and i am Using Mq 2 gas sensor Library .The problem is that how assign threshold limit in seketch and i am using alarm when when ppm of gas increase over threshold alarm pin high of arduino . but my code not work alarm is not on when Ppm is greater than threshold
here is code

include <MQ2.h>

//change this with the pin that you use
int threshold = 100;
int pin = A0;
int lpg, co, smoke;
const int Alarm = 13;
MQ2 mq2(pin);

void setup() {
  Serial.begin(9600);

  mq2.begin();
}

void loop() {


  float* values = mq2.read(true); //set it false if you don't want to print the values in the Serial


 lpg = mq2.readLPG();

 if(lpg>threshold)
  { digitalWrite( Alarm, HIGH);//if limit has been reached, LED turns on as status indicator
  }
   else {
    digitalWrite( Alarm, LOW);
co = mq2.readCO();
if(co>threshold)
{ digitalWrite( Alarm, HIGH);//if limit has been reached, LED turns on as status indicator
  }
   else {
    digitalWrite( Alarm, LOW);
  
  smoke = mq2.readSmoke();
if(some>threshold)

  { digitalWrite( Alarm, HIGH);//if limit has been reached, LED turns on as status indicator
  }
   else {
    digitalWrite( Alarm, LOW);

  }
  delay(1000);
}
   }
}

for a start:

const int Alarm = 13;

If that means pin 13 is the alarm output, don't you need to set it as pinMode(Alarm, OUTPUT) in setup()?

Bundle of thanks my dear friend groundfungus for solving my problem .I am very thankfull to you and i appreciate your response and once again thank you very much.

My pleasure.