Smoke Detector using Gas Sensor

1int red_LED_PIN = 11;
2int green_LED_PIN = 9;
3int blue_LED_PIN =  10;
4int buzzer = 6;
5int smoke_detector = A0;
6int safety_lim = 60; //Sets  smoke density safe limit
7
8void setup() {
9  pinMode(red_LED_PIN, OUTPUT);
10  pinMode(green_LED_PIN, OUTPUT);
11  pinMode(blue_LED_PIN, OUTPUT);
12  pinMode(buzzer,  OUTPUT);
13  pinMode(smoke_detector, INPUT);
14  Serial.begin(9600); //baud rate
15}
16
17void  loop() {
18  int sensor_read = analogRead(smoke_detector); 
19  	//reads and  stores the reading from the detector in sensor_read
20
21  Serial.print("Smoke  Density: ");
22  Serial.println(sensor_read);
23  
24  if (sensor_read > safety_lim)
25    // Checks if reading is beyond safety limit
26  {
27	analogWrite(red_LED_PIN,255);
28    analogWrite(green_LED_PIN, 0);
29    tone(buzzer,500, 100); //piezo rings 
30  }
31  else
32  {
33    analogWrite(green_LED_PIN, 255);
34    analogWrite(red_LED_PIN,0);
35    noTone(buzzer); //peizo wont ring
36  }
37  delay(50);
38}