Problem with mq-135 sensor

So i started coding this simple project and im having no issues with the compiler, but the sensor output on the analogRead command only returns 0 or 1 depending on how i set the potentiometer on the sensor. heres the code

int SensorValue = analogRead (A5);
int SogliaSensore = 1;
int PinLedRosso = 2;
int PinLedBlu = 4;
int PinLedVerde = 7;

void setup() {
pinMode (PinLedRosso, OUTPUT);
pinMode (PinLedBlu, OUTPUT);
pinMode (PinLedVerde, OUTPUT);
pinMode (A5, INPUT);

void loop() {
analogRead (A5);
if (SensorValue > SogliaSensore) {
RGB_controller (255, 0, 0);
Serial.print ("Sensor: ");
Serial.println ("Gas Detected");
RGB_controller (0, 0, 255);
Serial.print ("Sensor: ");
Serial.println ("No Gas Detected");
void RGB_controller (int Luminosita_rosso, int Luminosita_blu, int Luminosita_verde) {
digitalWrite( PinLedRosso, Luminosita_rosso);
digitalWrite( PinLedBlu, Luminosita_blu);
digitalWrite( PinLedVerde, Luminosita_verde);

ty in advance

Please use code tags when posting code.

This line needs to be in the loop() function, not at the start of your program:

int SensorValue = analogRead (A5);

Here, you read the voltage on pin A5, but don't do anything with it.

analogRead (A5);

thanks a lot for the fast answer