The system operates as follows: The MQ-5/MQ-135 gas sensor continuously monitors the surrounding air for LPG, methane, propane, smoke, and other combustible gases. When gas concentration exceeds a predefined threshold, the Arduino Uno activates the buzzer for audible alerts and LED for visual alerts. The I2C LCD displays real-time gas concentration levels (in ppm). The ESP8266 module sends data to a cloud platform (Blynk/ThingSpeak), enabling remote monitoring and push notifications to mobile devices. This IoT integration builds upon the foundational work of Mahato et al. [16] by adding remote alert capabilities.

3.2 Component Specifications

A. MQ-5 / MQ-135 Gas Sensor

The MQ-5 sensor is specifically designed for detecting LPG, propane, and methane, while the MQ-135 detects a broader range of gases including smoke, CO₂, alcohol, benzene, and ammonia [4][6][16]. As demonstrated by Mahato et al. [16], the MQ-5 sensor provides reliable detection of LPG leaks in household environments. Key specifications include:

Pin Connections:

·         VCC → 5V (Arduino)

·         GND → GND

·         AOUT (Analog Output) → Arduino Analog Pin A0

B. Arduino Uno Microcontroller

The Arduino Uno is an open-source microcontroller board based on the ATmega328P. It features 14 digital I/O pins, 6 analog inputs, 16 MHz clock speed, and USB programming capability [12]. It reads the analog voltage from the gas sensor, converts it to gas concentration (ppm), compares it with the threshold, and controls the buzzer, LED, and LCD.

C. Buzzer (Piezoelectric)

A 5V piezoelectric buzzer produces a loud beep (85-95 dB) when gas levels exceed the threshold, providing immediate audible warning to household members [7][8][16].

D. LED Indicators

·         Green LED: Indicates normal conditions (gas level < threshold)

·         Red LED: Indicates gas leakage detected (gas level > threshold)

E. I2C LCD Display (16×2)

A 16×2 I2C LCD displays real-time gas concentration in ppm and system status. The I2C interface reduces wiring to just SDA and SCL lines [10].

F. ESP8266 Wi-Fi Module

The ESP8266 is a low-cost Wi-Fi-enabled microcontroller used for IoT connectivity. It connects to the local Wi-Fi network and sends gas sensor data to cloud platforms (Blynk, ThingSpeak, or Firebase) for remote monitoring and push notifications [5][11].

G. Power Supply (9V Battery / 12V Adapter)

The system can be powered by a 9V battery (for portability) or a 12V DC adapter (for continuous home use).

3.3 Cost Analysis

Table 2 presents the detailed cost breakdown. Compared to commercial systems and even the basic system by Mahato et al. [16], the proposed system offers additional IoT features at a minimal cost increase.

Table 2: Cost and specifications

Average total cost: Approximately ₹900

4. Hardware Implementation

Fig. 2. Circuit Schematic Diagram of Household Gas Monitoring System

Table 3: Pin Connections

Fig. 3. Complete Hardware Model of Household Gas Monitoring System

4.1 Software Algorithm (Arduino Code)

#include <LiquidCrystal_I2C.h>

#include <ESP8266WiFi.h>

#include <BlynkSimpleEsp8266.h>

// Threshold settings

#define GAS_THRESHOLD 300 // ppm threshold for alert

#define SENSOR_PIN A0 // MQ-5/MQ-135 connected to A0

#define BUZZER_PIN 8 // Buzzer connected to D8

#define RED_LED 7 // Red LED connected to D7

#define GREEN_LED 6 // Green LED connected to D6

// Wi-Fi credentials

char ssid[] = "Your_WiFi_Name";

char pass[] = "Your_WiFi_Password";

LiquidCrystal_I2C lcd(0x27, 16, 2);

void setup() {

  pinMode(BUZZER_PIN, OUTPUT);

  pinMode(RED_LED, OUTPUT);

  pinMode(GREEN_LED, OUTPUT);

  lcd.init();

  lcd.backlight();

  lcd.setCursor(0, 0);

  lcd.print("Gas Monitor");

  lcd.setCursor(0, 1);

  lcd.print("System Ready");

    Serial.begin(9600);

  WiFi.begin(ssid, pass);

  delay(2000);

  lcd.clear();}

void loop() {

  int sensorValue = analogRead(SENSOR_PIN);

  int gas_ppm = map(sensorValue, 0, 1023, 0, 1000); // Convert to ppm

  lcd.setCursor(0, 0);

  lcd.print("Gas: ");

  lcd.print(gas_ppm);

  lcd.print(" ppm ");

  if (gas_ppm > GAS_THRESHOLD) {

    // Gas detected - Alert mode

    digitalWrite(RED_LED, HIGH);

    digitalWrite(GREEN_LED, LOW);

    digitalWrite(BUZZER_PIN, HIGH);

    lcd.setCursor(0, 1);

    lcd.print("GAS LEAKAGE!!! ");

    delay(1000);

    digitalWrite(BUZZER_PIN, LOW);

    delay(500);

    // Send alert to cloud

    Blynk.virtualWrite(V1, gas_ppm);

    Blynk.notify("ALERT: Gas Leakage Detected!"); } 

  else {

    // Normal condition

    digitalWrite(RED_LED, LOW);

    digitalWrite(GREEN_LED, HIGH);

    digitalWrite(BUZZER_PIN, LOW);

    lcd.setCursor(0, 1);

    lcd.print("Safe - Normal  ");  }

  delay(1000); // Update every second}

4.2 IoT Cloud Integration (Blynk/ThingSpeak)

The ESP8266 module sends gas concentration data to the Blynk cloud platform. Users can:

·         Monitor real-time gas levels on mobile dashboard

·         Receive push notifications when gas leakage is detected

·         View historical data and trends

·         Remotely check system status

This IoT capability represents a significant enhancement over previous work by Mahato et al. [16], who implemented only local alerts without remote monitoring features.

5. Results And Discussion

5.1 Experimental Setup

The prototype was tested under various gas concentration conditions, similar to the methodology employed by Mahato et al. [16] but with additional IoT performance evaluation:

Table 4 : Gas Concentration Level

Table 5: Experimental Results

5.2 Key Findings

1.       Detection Accuracy: The system successfully detected gas leakage in 18 out of 20 trials (90% accuracy)

2.       Response Time: Average detection time was 3-8 seconds depending on proximity and concentration

3.       Effective Range: The sensor reliably detected gas within 1-2 meters

4.       Remote Notification: Cloud alerts were received within 5-10 seconds of detection

5.       False Alarms: No false alarms occurred during normal room conditions

5.3 Comparison with Previous Work

Table 6: Comparative Analysis With Existing Work

The proposed system builds upon the foundational work of Mahato et al. [16] by adding IoT capabilities for remote monitoring and cloud-based alerts, while maintaining affordability. The Digital Umbrella concept by Kumar et al. [17] inspired the integration of multiple alert mechanisms in a compact, user-friendly design.

5.4 Applications

The proposed gas monitoring system is suitable for:

1.       Residential Kitchens: LPG gas leakage detection

2.       Industrial Kitchens: Restaurants, hostels, canteens

3.       Laboratories: Chemical gas detection

4.       Warehouses: Storage areas with combustible materials

5.       Boiler Rooms: Methane and propane detection

5.5 Limitations

1.       Limited Range: Effective detection within 1-2 meters from sensor

2.       No Gas Valve Control: Cannot automatically shut off gas supply

3.       Calibration Required: Sensor needs 10-15 minutes preheating

4.       Internet Dependency: Cloud alerts require active Wi-Fi

5.       False Positives: Cooking fumes may occasionally trigger sensor (requires threshold tuning)

6. Conclusion And Future Scope

6.1 Conclusion

This paper successfully presented the design and implementation of a low-cost, IoT-based household gas monitoring and leakage detection system. Building upon the foundational work of Mahato et al. in household gas monitoring and drawing inspiration from the integrated safety approach of Kumar et al. in the Digital Umbrella system, the proposed system adds significant IoT capabilities for remote monitoring.

The system utilizes an MQ-5/MQ-135 gas sensor for detecting LPG, propane, and combustible gases, an Arduino Uno microcontroller for data processing, a buzzer and LED for local alerts, an I2C LCD for real-time gas concentration display, and an ESP8266 Wi-Fi module for IoT connectivity.

Key achievements include:

1.       Successful detection of gas leakage within 3-8 seconds

2.       Real-time gas concentration display in ppm on LCD

3.       Dual alerts (audible buzzer + visual LED)

4.       IoT-enabled remote monitoring via mobile app (Blynk/ThingSpeak)

5.       Low-cost implementation at approximately ₹900 (USD 11)

This system adds remote monitoring and cloud notification capabilities. Compared to commercial systems costing ₹2,000-5,000, this system is significantly more affordable while offering superior IoT features.

6.2 Future Enhancements

1.       Automatic Gas Valve Shut-off: Add servo motor to close LPG cylinder regulator automatically

2.       SMS Alerts: Add GSM module (SIM800) for cellular notifications without Wi-Fi

3.       Exhaust Fan Control: Automatically turn on exhaust fan during gas leakage

4.       Multiple Sensors: Network multiple gas sensors for larger kitchens

5.       Voice Alert: Add voice module for verbal warnings in regional languages

6.       Battery Backup: Add rechargeable Li-ion battery for power outage protection

7.       Data Logging: Add SD card module for recording gas levels over time

Acknowledgment

The authors sincerely thank Prof. (Dr.) Pankaj Jha, Head of the Department of Electronics and Communication Engineering, IIMT College of Engineering, Greater Noida, for his invaluable guidance and support. The authors also acknowledge the faculty members, technical staff, and B.Tech. batchmates for their constructive feedback and laboratory facilities.