Gas Leakage Detector using Arduino and GSM Module with SMS Alert and Sound Alarm

We have published lots of interesting arduino projects like GSM based Fire Alarm System , Line Following Robot, RFID Based Access Control System and many other useful projects. This time, we are publishing a highly useful home application – Gas Leakage Detector using Arduino and GSM Module with SMS Alert and Sound Alarm.  We have published an LPG  Sensor Project using Arduino and MQ2 sensor before – which senses lpg leak and produces sound alarm. The project also has a relay system which turns ON or OFF a particular device upon gas leak (say we can turn the main electrical supply OFF upon gas leak to prevent fire).

So let’s come to our project!

Objectives of the Project

  • Detect Gas Leakage (like LPG leak, Butane leak, Methane leak) or any such petroleum based gaseous substance that can be detected using MQ5 Sensor.
  • Setup an SMS based Alert Mechanism and send 3 SMS (3 alert messages) to 2 specified mobile numbers (input inside the arduino program)
  • Produce a sound alarm upon gas leak and stop the alarm once gas leak is under control (gas presence in atmosphere is under normal range)
  • Display status in an LCD using a 16×2 LCD module.

Lets begin to build our project – Gas/LPG leakage detector with SMS Alert and Sound Alarm!.

I recommend you read the following tutorials before building this project!

1. Interfacing MQ5 Sensor to Arduino – teaches you how to interface MQ5 LPG sensor to Arduino and read values using analog or digital out pins of the MQ5 module.

2. Interfacing GSM Module to Arduino – teaches you how to interface a GSM module to Arduino and send/receive text messages using AT Commands.

GSM Module – Buyers Guide – are you looking to buy a GSM module? There are a handful of product variants for GSM module – like SIM900, SIM300, SIM800 etc. We have created this buyers guide to help you select the right GSM module for your project needs.

Circuit Diagram – Gas Leakage Detector using Arduino with GSM Module

Gas Leakage Detector using Arduino and GSM Module with Sound Alarm

Assemble the circuit as shown in diagram! Important connections are explained below.A photograph of the assembled circuit is shown below.

Gas Leakage Detector using Arduino


Note:- The speaker is not shown in this photograph. Anyway you can wire the speaker as shown in circuit diagram and connect it to pin 8 of arduino.

The Program/Code

#include <SoftwareSerial.h>
#include <LiquidCrystal.h>
LiquidCrystal lcd(12, 11, 5, 4, 3, 2); 
SoftwareSerial mySerial(9, 10);

int sensor=7;
int speaker=8;
int gas_value,Gas_alert_val, Gas_shut_val;
int Gas_Leak_Status;
int sms_count=0;

void setup()



void loop()

void CheckGas()

lcd.print("Gas Scan - ON");
 SetAlert(); // Function to send SMS Alerts

int ScanGasLevel()
gas_value=digitalRead(sensor); // reads the sensor output (Vout of LM35)

return gas_value; // returns temperature value in degree celsius

void SetAlert()
while(sms_count<3) //Number of SMS Alerts to be sent
SendTextMessage(); // Function to send AT Commands to GSM module
lcd.print("Gas Alert! SMS Sent!");

void CheckShutDown()


lcd.print("No Gas Leaking");

void SendTextMessage()
  mySerial.println("AT+CMGF=1");    //To send SMS in Text Mode
  mySerial.println("AT+CMGS=\"+919495xxxxxx\"\r"); // change to the phone number you using 
  mySerial.println("Gas Leaking!");//the content of the message
  mySerial.println((char)26);//the stopping character
   mySerial.println("AT+CMGS=\"+918113xxxxxx\"\r"); // change to the phone number you using 
  mySerial.println("Gas Leaking!");//the content of the message
  mySerial.println((char)26);//the message stopping character

Applying ‘gas leak’ using a cigarette lighter – refer photograph

Gas leakage detector using GSM module

Important Aspects about the Program

When we develop critical systems like Gas Leakage Detector or similar systems like Fire Alarm System, we need to monitor the sensor parameters continuously(24×7). So our system must monitor “gas leak” continuously.This is achieved by scanning the sensor output (digital out of MQ5) continuously inside the ScanGasLevel() subroutine. If you look into the program, the main function loop() has only two subroutines – CheckGas() and CheckShutDown() – which are called repeatedly. CheckGas() – is a subroutine which scans sensor output continuously and take actions if there occurs a ‘gas leak’ at any point of time.  CheckShutDown() – is a subroutine to monitor the shut down process and check if status of room is back to normal conditions (no gas leaking).

CheckGas() – is the function which monitors occurrence of a gas leak 24×7.  This function fetches the gas level measured by MQ35 (by reading digital out of MQ35 using digitalRead() command) and stores it to the variable Gas_alert_val for comparison. If there is no ‘gas leak’ – the sensor out will be HIGH. If there occurs a ‘gas leak’ at any point of time, the sensor out will immediately change to LOW status. The statement  if(Gas_alert_val==LOW) checks this and if a gas leak occurs, then an inner subroutine SetAlert() will be invoked.

 SetAlert() is the function that controls number of SMS alerts sent to each mobile number loaded in the program. The number of SMS alerts sent can be altered by changing the stopping condition of while loop. The stopping condition sms_count<3 – means 3 SMS alerts will be sent to each mobile number. If you want to send 5 alerts, just change the stopping condition to sms_count<5 – you got it ?  The function to send SMS (using AT Commands) – SendTextMessage() will be called 3 times if SMS alert count is 3. This function SendTextMessage() will be invoked as many times as the number SMS alerts set in the program. In addition to sending SMS alerts, this subroutine also controls the sound alarm. The alarm is invoked using command digitalWrite(speaker,HIGH) – which will activate the speaker connected at pin 8 of arduino.

Note:- We have limited the number of SMS alerts using the stopping condition. Once a gas leak occurs and the set number of SMS alerts has been sent, the system will not send any more SMS! The system assumes that its job is over by sending SMS. Humans has to come and shut down the gas leak problem. After sending alerts, the system will start monitoring Shut Down process. Once the gas leak has been eliminated, system will automatically reactivate its SMS alert settings by resetting the sms_count variable back to zero.

The output after applying ‘gas leak’ is shown in photograph!

Gas leakage detector with sms alert


Here is a video demonstration of the output!

CheckShutDown() – is the function which monitors if gas leak was shut down. We need to entertain this function only if a ‘gas leak’ has occurred. To limit the entry to the statements inside this routine, we have introduced a variable Gas_Leak_Status. This variable value will be set to value 1 when a gas leak occurs (check the statement inside SetAlert()). The statements inside CheckShutDown() will  be executed only if the value of Gas_Leak_Status==1. (If there was no gas leak occurred, we don’t need to waste time executing ShutDown checking statements). We consider the ‘gas leak’ has been eliminated once room temperature is back to normal. So if our variable Gas_shut_val falls back to HIGH status, we consider gas leak has been eliminated and surroundings are safe. The subroutine has statement to stop the gas leakage alarm (refer statement – digitalWrite(speaker,LOW) – which cuts the supply to pin 8 of arduino and stops the sound alarm) which will be executed when gas leak is eliminated completely (as the status of Gas_shut_val == HIGH). We start our Gas Leakage monitoring again with SMS Alerts active! (We reset the Gas_Leak_Status variable and sms_count variable back to zero – which are essential variable conditions for monitoring gas leak again and to send alert sms if gas leak repeats.

Here is a slideshare presentation of the project!

Show Comments

8 thoughts on “Gas Leakage Detector using Arduino and GSM Module with SMS Alert and Sound Alarm

  1. mat

    hello..this mini project its sale?can i buy this because i dont know how to make it..please email me.

      • saurabh

        is it working…….? if i add LED at pin 8 then without sensing LPG it is glowing…….can u please tell how it is working…….please send me the detail….

  2. Bhavani

    Vanakam jojo.this is very useful. I need a code for lpg leakage detector with arduino uno and Gsm with mq2 sensor without using lcd display.pls help me with ur code jojo


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