diff --git a/examples/MQ-131/MQ-131.ino b/examples/MQ-131/MQ-131.ino
index 0705917..f99378a 100644
--- a/examples/MQ-131/MQ-131.ino
+++ b/examples/MQ-131/MQ-131.ino
@@ -26,6 +26,7 @@
 #define pin A0 //Analog input 0 of your arduino
 #define type "MQ-131" //MQ131
 #define ADC_Bit_Resolution 10 // For arduino UNO/MEGA/NANO
+#define RatioMQ131CleanAir 15 //RS / R0 = 15 ppm
 //#define calibration_button 13 //Pin to calibrate your sensor
 
 //Declare Sensor
@@ -47,8 +48,28 @@ void setup() {
   O3      | 23.943 | -1.11
   */
 
-  // Calibration setup
-  MQ131.setR0(385.40);
+  
+  /*****************************  MQ CAlibration ********************************************/ 
+  // Explanation: 
+  // In this routine the sensor will measure the resistance of the sensor supposing before was pre-heated
+  // and now is on clean air (Calibration conditions), and it will setup R0 value.
+  // We recomend execute this routine only on setup or on the laboratory and save on the eeprom of your arduino
+  // This routine not need to execute to every restart, you can load your R0 if you know the value
+  // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
+  Serial.print("Calibrating please wait.");
+  int calcR0 = 0;
+  for(int i = 0; i<=10; i ++)
+  {
+    MQ131.update(); // Update data, the arduino will be read the voltage on the analog pin
+    calcR0 += MQ131.calibrate(RatioMQ131CleanAir);
+    Serial.print(".");
+  }
+  MQ131.setR0(calcR0/10);
+  Serial.println("  done!.");
+  
+  if(isinf(calcR0)) {Serial.println("Warning: Conection issue founded, R0 is infite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Conection issue founded, R0 is zero (Analog pin with short circuit to ground) please check your wiring and supply"); while(1);}
+  /*****************************  MQ CAlibration ********************************************/ 
 
   /* 
     //If the RL value is different from 10K please assign your RL value with the following method:
diff --git a/examples/MQ-135/MQ-135.ino b/examples/MQ-135/MQ-135.ino
index ee2ba02..22721b6 100644
--- a/examples/MQ-135/MQ-135.ino
+++ b/examples/MQ-135/MQ-135.ino
@@ -26,6 +26,7 @@
 #define pin A0 //Analog input 0 of your arduino
 #define type "MQ-135" //MQ135
 #define ADC_Bit_Resolution 10 // For arduino UNO/MEGA/NANO
+#define RatioMQ135CleanAir 3.6//RS / R0 = 3.6 ppm  
 //#define calibration_button 13 //Pin to calibrate your sensor
 
 //Declare Sensor
@@ -50,8 +51,28 @@ void setup() {
   Acetona  | 34.668 | -3.369
   */
 
-  // Calibration setup
-  MQ135.setR0(76.63);
+  
+  /*****************************  MQ CAlibration ********************************************/ 
+  // Explanation: 
+  // In this routine the sensor will measure the resistance of the sensor supposing before was pre-heated
+  // and now is on clean air (Calibration conditions), and it will setup R0 value.
+  // We recomend execute this routine only on setup or on the laboratory and save on the eeprom of your arduino
+  // This routine not need to execute to every restart, you can load your R0 if you know the value
+  // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
+  Serial.print("Calibrating please wait.");
+  int calcR0 = 0;
+  for(int i = 0; i<=10; i ++)
+  {
+    MQ135.update(); // Update data, the arduino will be read the voltage on the analog pin
+    calcR0 += MQ135.calibrate(RatioMQ135CleanAir);
+    Serial.print(".");
+  }
+  MQ135.setR0(calcR0/10);
+  Serial.println("  done!.");
+  
+  if(isinf(calcR0)) {Serial.println("Warning: Conection issue founded, R0 is infite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Conection issue founded, R0 is zero (Analog pin with short circuit to ground) please check your wiring and supply"); while(1);}
+  /*****************************  MQ CAlibration ********************************************/ 
 
   /* 
     //If the RL value is different from 10K please assign your RL value with the following method:
diff --git a/examples/MQ-2/MQ-2.ino b/examples/MQ-2/MQ-2.ino
index 2cff3ea..7bd9276 100644
--- a/examples/MQ-2/MQ-2.ino
+++ b/examples/MQ-2/MQ-2.ino
@@ -26,7 +26,7 @@
 #define pin A0 //Analog input 0 of your arduino
 #define type "MQ-2" //MQ2
 #define ADC_Bit_Resolution 10 // For arduino UNO/MEGA/NANO
-//#define calibration_button 13 //Pin to calibrate your sensor
+#define RatioMQ2CleanAir 9.83 //RS / R0 = 9.83 ppm 
 
 //Declare Sensor
 MQUnifiedsensor MQ2(placa, Voltage_Resolution, ADC_Bit_Resolution, pin, type);
@@ -48,9 +48,27 @@ void setup() {
     Propane| 658.71 | -2.168
   */
 
-  // Calibration setup
-  MQ2.setR0(9.659574468);
-
+  /*****************************  MQ CAlibration ********************************************/ 
+  // Explanation: 
+  // In this routine the sensor will measure the resistance of the sensor supposing before was pre-heated
+  // and now is on clean air (Calibration conditions), and it will setup R0 value.
+  // We recomend execute this routine only on setup or on the laboratory and save on the eeprom of your arduino
+  // This routine not need to execute to every restart, you can load your R0 if you know the value
+  // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
+  Serial.print("Calibrating please wait.");
+  int calcR0 = 0;
+  for(int i = 0; i<=10; i ++)
+  {
+    MQ2.update(); // Update data, the arduino will be read the voltage on the analog pin
+    calcR0 += MQ2.calibrate(RatioMQ2CleanAir);
+    Serial.print(".");
+  }
+  MQ2.setR0(calcR0/10);
+  Serial.println("  done!.");
+  
+  if(isinf(calcR0)) {Serial.println("Warning: Conection issue founded, R0 is infite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Conection issue founded, R0 is zero (Analog pin with short circuit to ground) please check your wiring and supply"); while(1);}
+  /*****************************  MQ CAlibration ********************************************/ 
   /* 
     //If the RL value is different from 10K please assign your RL value with the following method:
     MQ2.setRL(10);
diff --git a/examples/MQ-3/MQ-3.ino b/examples/MQ-3/MQ-3.ino
index 1eedbad..58ddea2 100644
--- a/examples/MQ-3/MQ-3.ino
+++ b/examples/MQ-3/MQ-3.ino
@@ -26,6 +26,7 @@
 #define pin A0 //Analog input 0 of your arduino
 #define type "MQ-3" //MQ3
 #define ADC_Bit_Resolution 10 // For arduino UNO/MEGA/NANO
+#define RatioMQ3CleanAir 60   //RS / R0 = 60 ppm 
 //#define calibration_button 13 //Pin to calibrate your sensor
 
 //Declare Sensor
@@ -49,8 +50,28 @@ void setup() {
   Hexane | 7585.3 | -2.849
   */
 
-  // Calibration setup
-  MQ3.setR0(3.86018237);
+  
+  /*****************************  MQ CAlibration ********************************************/ 
+  // Explanation: 
+  // In this routine the sensor will measure the resistance of the sensor supposing before was pre-heated
+  // and now is on clean air (Calibration conditions), and it will setup R0 value.
+  // We recomend execute this routine only on setup or on the laboratory and save on the eeprom of your arduino
+  // This routine not need to execute to every restart, you can load your R0 if you know the value
+  // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
+  Serial.print("Calibrating please wait.");
+  int calcR0 = 0;
+  for(int i = 0; i<=10; i ++)
+  {
+    MQ3.update(); // Update data, the arduino will be read the voltage on the analog pin
+    calcR0 += MQ3.calibrate(RatioMQ3CleanAir);
+    Serial.print(".");
+  }
+  MQ3.setR0(calcR0/10);
+  Serial.println("  done!.");
+  
+  if(isinf(calcR0)) {Serial.println("Warning: Conection issue founded, R0 is infite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Conection issue founded, R0 is zero (Analog pin with short circuit to ground) please check your wiring and supply"); while(1);}
+  /*****************************  MQ CAlibration ********************************************/ 
 
   /* 
     //If the RL value is different from 10K please assign your RL value with the following method:
diff --git a/examples/MQ-303A/MQ303.ino b/examples/MQ-303A/MQ303.ino
index fc1657e..fe96e03 100644
--- a/examples/MQ-303A/MQ303.ino
+++ b/examples/MQ-303A/MQ303.ino
@@ -26,6 +26,7 @@
 #define pin A0 //Analog input 0 of your arduino
 #define type "MQ-303" //MQ303
 #define ADC_Bit_Resolution 10 // For arduino UNO/MEGA/NANO
+#define RatioMQ303CleanAir 1  //RS / R0 = 1 ppm    
 //#define calibration_button 13 //Pin to calibrate your sensor
 
 //Declare Sensor
@@ -47,8 +48,28 @@ void setup() {
   Ethanol    | 3.4916 | -2.432
   */
 
-  // Calibration setup
-  MQ303.setR0(10);
+  
+  /*****************************  MQ CAlibration ********************************************/ 
+  // Explanation: 
+  // In this routine the sensor will measure the resistance of the sensor supposing before was pre-heated
+  // and now is on clean air (Calibration conditions), and it will setup R0 value.
+  // We recomend execute this routine only on setup or on the laboratory and save on the eeprom of your arduino
+  // This routine not need to execute to every restart, you can load your R0 if you know the value
+  // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
+  Serial.print("Calibrating please wait.");
+  int calcR0 = 0;
+  for(int i = 0; i<=10; i ++)
+  {
+    MQ303.update(); // Update data, the arduino will be read the voltage on the analog pin
+    calcR0 += MQ303.calibrate(RatioMQ303CleanAir);
+    Serial.print(".");
+  }
+  MQ303.setR0(calcR0/10);
+  Serial.println("  done!.");
+  
+  if(isinf(calcR0)) {Serial.println("Warning: Conection issue founded, R0 is infite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Conection issue founded, R0 is zero (Analog pin with short circuit to ground) please check your wiring and supply"); while(1);}
+  /*****************************  MQ CAlibration ********************************************/ 
 
   /* 
     //If the RL value is different from 10K please assign your RL value with the following method:
diff --git a/examples/MQ-309A/MQ-309.ino b/examples/MQ-309A/MQ-309.ino
index e5588de..951b2af 100644
--- a/examples/MQ-309A/MQ-309.ino
+++ b/examples/MQ-309A/MQ-309.ino
@@ -26,6 +26,7 @@
 #define pin A0 //Analog input 0 of your arduino
 #define type "MQ-309" //MQ309
 #define ADC_Bit_Resolution 10 // For arduino UNO/MEGA/NANO
+#define RatioMQ309CleanAir 11 //RS / R0 = 11 ppm 
 //#define calibration_button 13 //Pin to calibrate your sensor
 
 //Declare Sensor
@@ -48,8 +49,28 @@ void setup() {
   ALCOHOL | 473622  | -3.647
   */
 
-  // Calibration setup
-  MQ309.setR0(10);
+  
+  /*****************************  MQ CAlibration ********************************************/ 
+  // Explanation: 
+  // In this routine the sensor will measure the resistance of the sensor supposing before was pre-heated
+  // and now is on clean air (Calibration conditions), and it will setup R0 value.
+  // We recomend execute this routine only on setup or on the laboratory and save on the eeprom of your arduino
+  // This routine not need to execute to every restart, you can load your R0 if you know the value
+  // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
+  Serial.print("Calibrating please wait.");
+  int calcR0 = 0;
+  for(int i = 0; i<=10; i ++)
+  {
+    MQ309.update(); // Update data, the arduino will be read the voltage on the analog pin
+    calcR0 += MQ309.calibrate(RatioMQ309CleanAir);
+    Serial.print(".");
+  }
+  MQ309.setR0(calcR0/10);
+  Serial.println("  done!.");
+  
+  if(isinf(calcR0)) {Serial.println("Warning: Conection issue founded, R0 is infite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Conection issue founded, R0 is zero (Analog pin with short circuit to ground) please check your wiring and supply"); while(1);}
+  /*****************************  MQ CAlibration ********************************************/ 
 
   /* 
     //If the RL value is different from 10K please assign your RL value with the following method:
diff --git a/examples/MQ-4/MQ-4.ino b/examples/MQ-4/MQ-4.ino
index 727a880..51000ca 100644
--- a/examples/MQ-4/MQ-4.ino
+++ b/examples/MQ-4/MQ-4.ino
@@ -26,6 +26,7 @@
 #define pin A0 //Analog input 0 of your arduino
 #define type "MQ-4" //MQ4
 #define ADC_Bit_Resolution 10 // For arduino UNO/MEGA/NANO
+#define RatioMQ4CleanAir 4.4  //RS / R0 = 4.4 ppm 
 //#define calibration_button 13 //Pin to calibrate your sensor
 
 //Declare Sensor
@@ -49,8 +50,28 @@ void setup() {
   */
 
   
-  // Calibration setup
-  MQ4.setR0(3.86018237);
+  
+  /*****************************  MQ CAlibration ********************************************/ 
+  // Explanation: 
+  // In this routine the sensor will measure the resistance of the sensor supposing before was pre-heated
+  // and now is on clean air (Calibration conditions), and it will setup R0 value.
+  // We recomend execute this routine only on setup or on the laboratory and save on the eeprom of your arduino
+  // This routine not need to execute to every restart, you can load your R0 if you know the value
+  // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
+  Serial.print("Calibrating please wait.");
+  int calcR0 = 0;
+  for(int i = 0; i<=10; i ++)
+  {
+    MQ4.update(); // Update data, the arduino will be read the voltage on the analog pin
+    calcR0 += MQ4.calibrate(RatioMQ4CleanAir);
+    Serial.print(".");
+  }
+  MQ4.setR0(calcR0/10);
+  Serial.println("  done!.");
+  
+  if(isinf(calcR0)) {Serial.println("Warning: Conection issue founded, R0 is infite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Conection issue founded, R0 is zero (Analog pin with short circuit to ground) please check your wiring and supply"); while(1);}
+  /*****************************  MQ CAlibration ********************************************/ 
 
   /* 
     //If the RL value is different from 10K please assign your RL value with the following method:
diff --git a/examples/MQ-5/MQ-5.ino b/examples/MQ-5/MQ-5.ino
index dd1106a..d0b7c13 100644
--- a/examples/MQ-5/MQ-5.ino
+++ b/examples/MQ-5/MQ-5.ino
@@ -26,6 +26,7 @@
 #define pin A0 //Analog input 0 of your arduino
 #define type "MQ-5" //MQ5
 #define ADC_Bit_Resolution 10 // For arduino UNO/MEGA/NANO
+#define RatioMQ5CleanAir 6.5  //RS / R0 = 6.5 ppm 
 //#define calibration_button 13 //Pin to calibrate your sensor
 
 //Declare Sensor
@@ -48,8 +49,28 @@ void setup() {
   Alcohol| 97124  | -4.918
   */
   
-  // Calibration setup
-  MQ5.setR0(71.100304);
+  
+  /*****************************  MQ CAlibration ********************************************/ 
+  // Explanation: 
+  // In this routine the sensor will measure the resistance of the sensor supposing before was pre-heated
+  // and now is on clean air (Calibration conditions), and it will setup R0 value.
+  // We recomend execute this routine only on setup or on the laboratory and save on the eeprom of your arduino
+  // This routine not need to execute to every restart, you can load your R0 if you know the value
+  // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
+  Serial.print("Calibrating please wait.");
+  int calcR0 = 0;
+  for(int i = 0; i<=10; i ++)
+  {
+    MQ5.update(); // Update data, the arduino will be read the voltage on the analog pin
+    calcR0 += MQ5.calibrate(RatioMQ5CleanAir);
+    Serial.print(".");
+  }
+  MQ5.setR0(calcR0/10);
+  Serial.println("  done!.");
+  
+  if(isinf(calcR0)) {Serial.println("Warning: Conection issue founded, R0 is infite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Conection issue founded, R0 is zero (Analog pin with short circuit to ground) please check your wiring and supply"); while(1);}
+  /*****************************  MQ CAlibration ********************************************/ 
 
   /* 
     //If the RL value is different from 10K please assign your RL value with the following method:
diff --git a/examples/MQ-6/MQ-6.ino b/examples/MQ-6/MQ-6.ino
index d2e9389..6302464 100644
--- a/examples/MQ-6/MQ-6.ino
+++ b/examples/MQ-6/MQ-6.ino
@@ -26,6 +26,7 @@
 #define pin A0 //Analog input 0 of your arduino
 #define type "MQ-6" //MQ6
 #define ADC_Bit_Resolution 10 // For arduino UNO/MEGA/NANO
+#define RatioMQ6CleanAir 10   //RS / R0 = 10 ppm 
 //#define calibration_button 13 //Pin to calibrate your sensor
 
 //Declare Sensor
@@ -48,9 +49,28 @@ void setup() {
   Alcohol | 50000000 | -6.017
   */
   
-  // Calibration setup
-  MQ6.setR0(13.4285714);
-
+  
+  /*****************************  MQ CAlibration ********************************************/ 
+  // Explanation: 
+  // In this routine the sensor will measure the resistance of the sensor supposing before was pre-heated
+  // and now is on clean air (Calibration conditions), and it will setup R0 value.
+  // We recomend execute this routine only on setup or on the laboratory and save on the eeprom of your arduino
+  // This routine not need to execute to every restart, you can load your R0 if you know the value
+  // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
+  Serial.print("Calibrating please wait.");
+  int calcR0 = 0;
+  for(int i = 0; i<=10; i ++)
+  {
+    MQ6.update(); // Update data, the arduino will be read the voltage on the analog pin
+    calcR0 += MQ6.calibrate(RatioMQ6CleanAir);
+    Serial.print(".");
+  }
+  MQ6.setR0(calcR0/10);
+  Serial.println("  done!.");
+  
+  if(isinf(calcR0)) {Serial.println("Warning: Conection issue founded, R0 is infite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Conection issue founded, R0 is zero (Analog pin with short circuit to ground) please check your wiring and supply"); while(1);}
+  /*****************************  MQ CAlibration ********************************************/ 
   /* 
     //If the RL value is different from 10K please assign your RL value with the following method:
     MQ6.setRL(10);
diff --git a/examples/MQ-7/MQ-7.ino b/examples/MQ-7/MQ-7.ino
index 6c86340..6bc96e1 100644
--- a/examples/MQ-7/MQ-7.ino
+++ b/examples/MQ-7/MQ-7.ino
@@ -26,6 +26,7 @@
 #define pin A0 //Analog input 0 of your arduino
 #define type "MQ-7" //MQ7
 #define ADC_Bit_Resolution 10 // For arduino UNO/MEGA/NANO
+#define RatioMQ7CleanAir 27.5 //RS / R0 = 27.5 ppm 
 //#define calibration_button 13 //Pin to calibrate your sensor
 
 //Declare Sensor
@@ -49,8 +50,28 @@ void setup() {
   Alcohol | 40000000000000000 | -12.35
   */
   
-  // Calibration setup
-  MQ7.setR0(4);
+  
+  /*****************************  MQ CAlibration ********************************************/ 
+  // Explanation: 
+  // In this routine the sensor will measure the resistance of the sensor supposing before was pre-heated
+  // and now is on clean air (Calibration conditions), and it will setup R0 value.
+  // We recomend execute this routine only on setup or on the laboratory and save on the eeprom of your arduino
+  // This routine not need to execute to every restart, you can load your R0 if you know the value
+  // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
+  Serial.print("Calibrating please wait.");
+  int calcR0 = 0;
+  for(int i = 0; i<=10; i ++)
+  {
+    MQ7.update(); // Update data, the arduino will be read the voltage on the analog pin
+    calcR0 += MQ7.calibrate(RatioMQ7CleanAir);
+    Serial.print(".");
+  }
+  MQ7.setR0(calcR0/10);
+  Serial.println("  done!.");
+  
+  if(isinf(calcR0)) {Serial.println("Warning: Conection issue founded, R0 is infite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Conection issue founded, R0 is zero (Analog pin with short circuit to ground) please check your wiring and supply"); while(1);}
+  /*****************************  MQ CAlibration ********************************************/ 
 
   /* 
     //If the RL value is different from 10K please assign your RL value with the following method:
diff --git a/examples/MQ-8/MQ-8.ino b/examples/MQ-8/MQ-8.ino
index f559a5b..383a06d 100644
--- a/examples/MQ-8/MQ-8.ino
+++ b/examples/MQ-8/MQ-8.ino
@@ -26,6 +26,7 @@
 #define pin A0 //Analog input 0 of your arduino
 #define type "MQ-8" //MQ8
 #define ADC_Bit_Resolution 10 // For arduino UNO/MEGA/NANO
+#define RatioMQ8CleanAir 70   //RS / R0 = 70 ppm  
 //#define calibration_button 13 //Pin to calibrate your sensor
 
 //Declare Sensor
@@ -49,9 +50,28 @@ void setup() {
   Alcohol | 76101 | -1.86
   */
   
-  // Calibration setup
-  MQ8.setR0(1);
 
+  /*****************************  MQ CAlibration ********************************************/ 
+  // Explanation: 
+  // In this routine the sensor will measure the resistance of the sensor supposing before was pre-heated
+  // and now is on clean air (Calibration conditions), and it will setup R0 value.
+  // We recomend execute this routine only on setup or on the laboratory and save on the eeprom of your arduino
+  // This routine not need to execute to every restart, you can load your R0 if you know the value
+  // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
+  Serial.print("Calibrating please wait.");
+  int calcR0 = 0;
+  for(int i = 0; i<=10; i ++)
+  {
+    MQ8.update(); // Update data, the arduino will be read the voltage on the analog pin
+    calcR0 += MQ8.calibrate(RatioMQ8CleanAir);
+    Serial.print(".");
+  }
+  MQ8.setR0(calcR0/10);
+  Serial.println("  done!.");
+  
+  if(isinf(calcR0)) {Serial.println("Warning: Conection issue founded, R0 is infite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Conection issue founded, R0 is zero (Analog pin with short circuit to ground) please check your wiring and supply"); while(1);}
+  /*****************************  MQ CAlibration ********************************************/ 
   /* 
     //If the RL value is different from 10K please assign your RL value with the following method:
     MQ8.setRL(10);
diff --git a/examples/MQ-9/MQ-9.ino b/examples/MQ-9/MQ-9.ino
index 8cd5926..276d6bc 100644
--- a/examples/MQ-9/MQ-9.ino
+++ b/examples/MQ-9/MQ-9.ino
@@ -26,6 +26,7 @@
 #define pin A0 //Analog input 0 of your arduino
 #define type "MQ-9" //MQ9
 #define ADC_Bit_Resolution 10 // For arduino UNO/MEGA/NANO
+#define RatioMQ9CleanAir 9.6  //RS / R0 = 9.6 ppm  
 //#define calibration_button 13 //Pin to calibrate your sensor
 
 //Declare Sensor
@@ -47,8 +48,28 @@ void setup() {
   CO      | 599.65 | -2.244
   */
 
-  // Calibration setup
-  MQ9.setR0(9.42857143);
+  
+  /*****************************  MQ CAlibration ********************************************/ 
+  // Explanation: 
+  // In this routine the sensor will measure the resistance of the sensor supposing before was pre-heated
+  // and now is on clean air (Calibration conditions), and it will setup R0 value.
+  // We recomend execute this routine only on setup or on the laboratory and save on the eeprom of your arduino
+  // This routine not need to execute to every restart, you can load your R0 if you know the value
+  // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
+  Serial.print("Calibrating please wait.");
+  int calcR0 = 0;
+  for(int i = 0; i<=10; i ++)
+  {
+    MQ9.update(); // Update data, the arduino will be read the voltage on the analog pin
+    calcR0 += MQ9.calibrate(RatioMQ9CleanAir);
+    Serial.print(".");
+  }
+  MQ9.setR0(calcR0/10);
+  Serial.println("  done!.");
+  
+  if(isinf(calcR0)) {Serial.println("Warning: Conection issue founded, R0 is infite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Conection issue founded, R0 is zero (Analog pin with short circuit to ground) please check your wiring and supply"); while(1);}
+  /*****************************  MQ CAlibration ********************************************/ 
 
   /* 
     //If the RL value is different from 10K please assign your RL value with the following method: