IoT-Based Fire Detection & Alert System

 

Build an advanced fire detection system with multiple sensors, instant alerts, and automatic response.

Key Features

• Smoke & flame detection
• Temperature monitoring
• SMS/Email/App alerts
• Automatic sprinkler activation
• Multi-zone monitoring

Diagram.json:

{

  "version": 1,

  "author": "IoT Fire Detection System",

  "editor": "wokwi",

  "parts": [

    {

      "type": "wokwi-esp32-devkit-v1",

      "id": "esp",

      "top": 0,

      "left": 0,

      "attrs": {}

    },

    {

      "type": "wokwi-dht22",

      "id": "dht1",

      "top": -86.4,

      "left": 124.8,

      "attrs": { "temperature": "30", "humidity": "50" }

    },

    {

      "type": "wokwi-potentiometer",

      "id": "smoke",

      "top": -19.2,

      "left": 297.6,

      "rotate": 180,

      "attrs": { "label": "Smoke Sensor (MQ-2)" }

    },

    {

      "type": "wokwi-potentiometer",

      "id": "flame",

      "top": 86.4,

      "left": 297.6,

      "rotate": 180,

      "attrs": { "label": "Flame Sensor" }

    },

    {

      "type": "wokwi-led",

      "id": "red_led",

      "top": -124.8,

      "left": 422.4,

      "attrs": { "color": "red", "lightColor": "red", "label": "DANGER" }

    },

    {

      "type": "wokwi-resistor",

      "id": "r1",

      "top": -67.2,

      "left": 422.4,

      "rotate": 90,

      "attrs": { "value": "220" }

    },

    {

      "type": "wokwi-led",

      "id": "green_led",

      "top": -124.8,

      "left": 499.2,

      "attrs": { "color": "green", "lightColor": "green", "label": "SAFE" }

    },

    {

      "type": "wokwi-resistor",

      "id": "r2",

      "top": -67.2,

      "left": 499.2,

      "rotate": 90,

      "attrs": { "value": "220" }

    },

    {

      "type": "wokwi-led",

      "id": "blue_led",

      "top": -124.8,

      "left": 576,

      "attrs": { "color": "blue", "lightColor": "blue", "label": "WARNING" }

    },

    {

      "type": "wokwi-resistor",

      "id": "r3",

      "top": -67.2,

      "left": 576,

      "rotate": 90,

      "attrs": { "value": "220" }

    },

    {

      "type": "wokwi-led",

      "id": "sprinkler",

      "top": 38.4,

      "left": 422.4,

      "attrs": { "color": "cyan", "lightColor": "cyan", "label": "Sprinkler" }

    },

    {

      "type": "wokwi-resistor",

      "id": "r4",

      "top": 96,

      "left": 422.4,

      "rotate": 90,

      "attrs": { "value": "220" }

    },

    {

      "type": "wokwi-led",

      "id": "fan",

      "top": 38.4,

      "left": 499.2,

      "attrs": { "color": "white", "lightColor": "white", "label": "Exhaust Fan" }

    },

    {

      "type": "wokwi-resistor",

      "id": "r5",

      "top": 96,

      "left": 499.2,

      "rotate": 90,

      "attrs": { "value": "220" }

    },

    {

      "type": "wokwi-buzzer",

      "id": "bz1",

      "top": 172.8,

      "left": 470.4,

      "attrs": { "volume": "0.5" }

    },

    {

      "type": "wokwi-ssd1306",

      "id": "oled1",

      "top": 192,

      "left": 249.6,

      "attrs": { "i2cAddress": "0x3C" }

    }

  ],

  "connections": [

    [ "esp:TX0", "$serialMonitor:RX", "", [] ],

    [ "esp:RX0", "$serialMonitor:TX", "", [] ],

   

    [ "dht1:VCC", "esp:3V3", "red", [ "v0" ] ],

    [ "dht1:GND", "esp:GND.1", "black", [ "v0" ] ],

    [ "dht1:SDA", "esp:D15", "green", [ "v0" ] ],

   

    [ "smoke:GND", "esp:GND.1", "black", [ "v0" ] ],

    [ "smoke:VCC", "esp:3V3", "red", [ "v0" ] ],

    [ "smoke:SIG", "esp:D34", "orange", [ "v0" ] ],

   

    [ "flame:GND", "esp:GND.2", "black", [ "v0" ] ],

    [ "flame:VCC", "esp:3V3", "red", [ "v0" ] ],

    [ "flame:SIG", "esp:D35", "yellow", [ "v0" ] ],

   

    [ "red_led:A", "esp:D26", "red", [ "v0" ] ],

    [ "red_led:C", "r1:1", "red", [ "v0" ] ],

    [ "r1:2", "esp:GND.1", "black", [ "v0" ] ],

   

    [ "green_led:A", "esp:D27", "green", [ "v0" ] ],

    [ "green_led:C", "r2:1", "green", [ "v0" ] ],

    [ "r2:2", "esp:GND.1", "black", [ "v0" ] ],

   

    [ "blue_led:A", "esp:D14", "blue", [ "v0" ] ],

    [ "blue_led:C", "r3:1", "blue", [ "v0" ] ],

    [ "r3:2", "esp:GND.1", "black", [ "v0" ] ],

   

    [ "sprinkler:A", "esp:D12", "cyan", [ "v0" ] ],

    [ "sprinkler:C", "r4:1", "cyan", [ "v0" ] ],

    [ "r4:2", "esp:GND.2", "black", [ "v0" ] ],

   

    [ "fan:A", "esp:D13", "white", [ "v0" ] ],

    [ "fan:C", "r5:1", "white", [ "v0" ] ],

    [ "r5:2", "esp:GND.2", "black", [ "v0" ] ],

   

    [ "bz1:1", "esp:D25", "purple", [ "v0" ] ],

    [ "bz1:2", "esp:GND.2", "black", [ "v0" ] ],

   

    [ "oled1:VCC", "esp:3V3", "red", [ "h0" ] ],

    [ "oled1:GND", "esp:GND.2", "black", [ "h0" ] ],

    [ "oled1:SDA", "esp:D21", "blue", [ "h0" ] ],

    [ "oled1:SCL", "esp:D22", "yellow", [ "h0" ] ]

  ],

  "dependencies": {}

}

Components Required

• ESP32 Board
• MQ-2 Smoke Sensor
• Flame Sensor (IR)
• DHT22 Temperature Sensor
• Buzzer & LED indicators
• GSM Module (optional)

Code:

/*

 * IoT-Based Fire Detection & Alert System

 *

 * Features:

 * - MQ-2 Gas/Smoke Sensor detection

 * - DHT22 Temperature & Humidity monitoring

 * - Flame sensor detection

 * - Multi-level alert system (Warning, Danger, Critical)

 * - Buzzer alarm with different patterns

 * - RGB LED visual indicators

 * - OLED display for status

 * - Web dashboard for remote monitoring

 * - SMS/Email alert simulation

 * - Automatic fire suppression trigger

 * - Data logging

 * - Real-time notifications

 */

#include <WiFi.h>

#include <WebServer.h>

#include <DHT.h>

#include <Wire.h>

#include <Adafruit_GFX.h>

#include <Adafruit_SSD1306.h>

// WiFi Credentials

const char* ssid = "Wokwi-GUEST";

const char* password = "";

// Web Server

WebServer server(80);

// Pin Definitions

#define DHT_PIN 15           // Temperature & Humidity sensor

#define MQ2_PIN 34           // Gas/Smoke sensor (analog)

#define FLAME_PIN 35         // Flame sensor (analog)

#define BUZZER_PIN 25        // Alarm buzzer

#define RED_LED_PIN 26       // Red LED (Danger)

#define GREEN_LED_PIN 27     // Green LED (Safe)

#define BLUE_LED_PIN 14      // Blue LED (Warning)

#define SPRINKLER_PIN 12     // Fire suppression system

#define EXHAUST_FAN_PIN 13   // Exhaust fan

// DHT Sensor

#define DHT_TYPE DHT22

DHT dht(DHT_PIN, DHT_TYPE);

// OLED Display

#define SCREEN_WIDTH 128

#define SCREEN_HEIGHT 64

#define OLED_RESET -1

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// Alert Levels

enum AlertLevel {

  SAFE,

  WARNING,

  DANGER,

  CRITICAL

};

// System State

struct SystemState {

  float temperature;

  float humidity;

  int smokeLevel;        // 0-100%

  int flameLevel;        // 0-100%

  AlertLevel alertLevel;

  bool sprinklerActive;

  bool exhaustFanActive;

  bool alarmActive;

  unsigned long lastAlert;

  int alertCount;

  String location;

};

SystemState fireSystem;

// Thresholds

const float TEMP_WARNING = 35.0;    // °C

const float TEMP_DANGER = 45.0;     // °C

const float TEMP_CRITICAL = 55.0;   // °C

const int SMOKE_WARNING = 30;       // %

const int SMOKE_DANGER = 50;        // %

const int SMOKE_CRITICAL = 70;      // %

const int FLAME_THRESHOLD = 40;     // %

// Timing

unsigned long lastSensorRead = 0;

unsigned long lastDisplayUpdate = 0;

unsigned long alarmStartTime = 0;

const long sensorInterval = 1000;

const long displayInterval = 500;

// Alert History

struct AlertLog {

  String timestamp;

  String level;

  float temp;

  int smoke;

  int flame;

};

AlertLog alertHistory[10];

int historyIndex = 0;

void setup() {

  Serial.begin(115200);

 

  // Initialize pins

  pinMode(BUZZER_PIN, OUTPUT);

  pinMode(RED_LED_PIN, OUTPUT);

  pinMode(GREEN_LED_PIN, OUTPUT);

  pinMode(BLUE_LED_PIN, OUTPUT);

  pinMode(SPRINKLER_PIN, OUTPUT);

  pinMode(EXHAUST_FAN_PIN, OUTPUT);

  pinMode(MQ2_PIN, INPUT);

  pinMode(FLAME_PIN, INPUT);

 

  // Initialize DHT

  dht.begin();

 

  // Initialize OLED

  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {

    Serial.println(F("OLED failed"));

  } else {

    display.clearDisplay();

    display.setTextSize(1);

    display.setTextColor(SSD1306_WHITE);

    display.setCursor(0, 0);

    display.println("FIRE DETECTION");

    display.println("SYSTEM");

    display.println("");

    display.println("Initializing...");

    display.display();

    delay(2000);

  }

 

  // Initialize system state

  fireSystem.temperature = 0;

  fireSystem.humidity = 0;

  fireSystem.smokeLevel = 0;

  fireSystem.flameLevel = 0;

  fireSystem.alertLevel = SAFE;

  fireSystem.sprinklerActive = false;

  fireSystem.exhaustFanActive = false;

  fireSystem.alarmActive = false;

  fireSystem.lastAlert = 0;

  fireSystem.alertCount = 0;

  fireSystem.location = "Building A - Floor 3";

 

  // Connect to WiFi

  WiFi.begin(ssid, password);

  Serial.print("Connecting to WiFi");

 

  display.clearDisplay();

  display.setCursor(0, 0);

  display.println("Connecting WiFi...");

  display.display();

 

  while (WiFi.status() != WL_CONNECTED) {

    delay(500);

    Serial.print(".");

  }

 

  Serial.println("\n✓ WiFi connected!");

  Serial.print("IP address: ");

  Serial.println(WiFi.localIP());

 

  // Setup web server routes

  server.on("/", handleRoot);

  server.on("/status", handleStatus);

  server.on("/history", handleHistory);

  server.on("/reset", handleReset);

  server.on("/test", handleTest);

  server.on("/silence", handleSilence);

 

  server.begin();

  Serial.println("✓ Web server started!");

 

  Serial.println("\n╔════════════════════════════════════╗");

  Serial.println("║  FIRE DETECTION SYSTEM ONLINE     ║");

  Serial.println("╚════════════════════════════════════╝");

  Serial.print("Access Dashboard: http://");

  Serial.println(WiFi.localIP());

  Serial.println();

 

  // System ready indicator

  setStatusLED(SAFE);

  playStartupTone();

}

void loop() {

  server.handleClient();

 

  unsigned long currentMillis = millis();

 

  // Read sensors

  if (currentMillis - lastSensorRead >= sensorInterval) {

    lastSensorRead = currentMillis;

    readSensors();

    evaluateFireRisk();

    controlSafetySystems();

  }

 

  // Update display

  if (currentMillis - lastDisplayUpdate >= displayInterval) {

    lastDisplayUpdate = currentMillis;

    updateDisplay();

  }

 

  // Handle alarm patterns

  if (fireSystem.alarmActive) {

    handleAlarm();

  }

}

void readSensors() {

  // Read temperature and humidity

  fireSystem.temperature = dht.readTemperature();

  fireSystem.humidity = dht.readHumidity();

 

  // Check for sensor errors

  if (isnan(fireSystem.temperature)) fireSystem.temperature = 0;

  if (isnan(fireSystem.humidity)) fireSystem.humidity = 0;

 

  // Read smoke sensor (MQ-2 simulation)

  int smokeRaw = analogRead(MQ2_PIN);

  fireSystem.smokeLevel = map(smokeRaw, 0, 4095, 0, 100);

 

  // Read flame sensor

  int flameRaw = analogRead(FLAME_PIN);

  fireSystem.flameLevel = map(flameRaw, 0, 4095, 100, 0); // Inverted

 

  // Print sensor readings

  if (fireSystem.alertLevel != SAFE) {

    Serial.println("┌─────────── SENSOR READINGS ───────────┐");

    Serial.print("│ Temperature: ");

    Serial.print(fireSystem.temperature, 1);

    Serial.println(" °C");

    Serial.print("│ Humidity: ");

    Serial.print(fireSystem.humidity, 1);

    Serial.println(" %");

    Serial.print("│ Smoke Level: ");

    Serial.print(fireSystem.smokeLevel);

    Serial.println(" %");

    Serial.print("│ Flame Detected: ");

    Serial.print(fireSystem.flameLevel);

    Serial.println(" %");

    Serial.println("└────────────────────────────────────────┘");

  }

}

void evaluateFireRisk() {

  AlertLevel previousLevel = fireSystem.alertLevel;

  AlertLevel newLevel = SAFE;

 

  // Critical conditions (immediate danger)

  if (fireSystem.temperature >= TEMP_CRITICAL ||

      fireSystem.smokeLevel >= SMOKE_CRITICAL ||

      fireSystem.flameLevel >= FLAME_THRESHOLD) {

    newLevel = CRITICAL;

  }

  // Danger conditions

  else if (fireSystem.temperature >= TEMP_DANGER ||

           fireSystem.smokeLevel >= SMOKE_DANGER) {

    newLevel = DANGER;

  }

  // Warning conditions

  else if (fireSystem.temperature >= TEMP_WARNING ||

           fireSystem.smokeLevel >= SMOKE_WARNING) {

    newLevel = WARNING;

  }

  // Safe

  else {

    newLevel = SAFE;

  }

 

  fireSystem.alertLevel = newLevel;

 

  // Alert level changed

  if (newLevel != previousLevel) {

    handleAlertChange(previousLevel, newLevel);

  }

}

void handleAlertChange(AlertLevel oldLevel, AlertLevel newLevel) {

  Serial.println("\n╔══════════════════════════════════════╗");

  Serial.print("║  ALERT LEVEL CHANGE: ");

  Serial.print(getAlertLevelName(oldLevel));

  Serial.print(" → ");

  Serial.println(getAlertLevelName(newLevel));

  Serial.println("╚══════════════════════════════════════╝");

 

  // Log alert

  logAlert();

 

  // Update visual indicators

  setStatusLED(newLevel);

 

  // Trigger alarm if danger detected

  if (newLevel >= DANGER && oldLevel < DANGER) {

    activateAlarm();

    sendAlert();

  }

 

  // Deactivate alarm if safe

  if (newLevel == SAFE && oldLevel != SAFE) {

    deactivateAlarm();

  }

}

void controlSafetySystems() {

  // Activate sprinkler for critical fire

  if (fireSystem.alertLevel == CRITICAL && !fireSystem.sprinklerActive) {

    activateSprinkler();

  } else if (fireSystem.alertLevel < CRITICAL && fireSystem.sprinklerActive) {

    deactivateSprinkler();

  }

 

  // Activate exhaust fan for smoke

  if (fireSystem.smokeLevel >= SMOKE_WARNING && !fireSystem.exhaustFanActive) {

    activateExhaustFan();

  } else if (fireSystem.smokeLevel < SMOKE_WARNING && fireSystem.exhaustFanActive) {

    deactivateExhaustFan();

  }

}

void activateSprinkler() {

  fireSystem.sprinklerActive = true;

  digitalWrite(SPRINKLER_PIN, HIGH);

  Serial.println("🚿 SPRINKLER SYSTEM ACTIVATED!");

}

void deactivateSprinkler() {

  fireSystem.sprinklerActive = false;

  digitalWrite(SPRINKLER_PIN, LOW);

  Serial.println("🚿 Sprinkler deactivated");

}

void activateExhaustFan() {

  fireSystem.exhaustFanActive = true;

  digitalWrite(EXHAUST_FAN_PIN, HIGH);

  Serial.println("💨 EXHAUST FAN ACTIVATED!");

}

void deactivateExhaustFan() {

  fireSystem.exhaustFanActive = false;

  digitalWrite(EXHAUST_FAN_PIN, LOW);

  Serial.println("💨 Exhaust fan deactivated");

}

void activateAlarm() {

  fireSystem.alarmActive = true;

  alarmStartTime = millis();

  Serial.println("🚨 ALARM ACTIVATED! 🚨");

}

void deactivateAlarm() {

  fireSystem.alarmActive = false;

  digitalWrite(BUZZER_PIN, LOW);

  Serial.println("✓ Alarm deactivated - System safe");

}

void handleAlarm() {

  unsigned long elapsed = millis() - alarmStartTime;

  int pattern = (elapsed / 200) % 4;

 

  if (fireSystem.alertLevel == CRITICAL) {

    // Fast continuous beeping

    digitalWrite(BUZZER_PIN, pattern < 2 ? HIGH : LOW);

  } else if (fireSystem.alertLevel == DANGER) {

    // Medium beeping

    digitalWrite(BUZZER_PIN, pattern < 1 ? HIGH : LOW);

  }

}

void setStatusLED(AlertLevel level) {

  // Turn off all LEDs

  digitalWrite(RED_LED_PIN, LOW);

  digitalWrite(GREEN_LED_PIN, LOW);

  digitalWrite(BLUE_LED_PIN, LOW);

 

  switch(level) {

    case SAFE:

      digitalWrite(GREEN_LED_PIN, HIGH);

      break;

    case WARNING:

      digitalWrite(BLUE_LED_PIN, HIGH);

      break;

    case DANGER:

      digitalWrite(RED_LED_PIN, HIGH);

      break;

    case CRITICAL:

      // Blink red rapidly

      digitalWrite(RED_LED_PIN, (millis() / 200) % 2);

      break;

  }

}

void updateDisplay() {

  display.clearDisplay();

  display.setTextSize(1);

  display.setCursor(0, 0);

 

  // Title

  display.println("FIRE DETECTION");

  display.drawLine(0, 9, 128, 9, SSD1306_WHITE);

 

  // Alert Status

  display.setCursor(0, 12);

  display.print("Status: ");

  display.println(getAlertLevelName(fireSystem.alertLevel));

 

  // Temperature

  display.setCursor(0, 22);

  display.print("Temp: ");

  display.print(fireSystem.temperature, 1);

  display.println(" C");

 

  // Smoke

  display.setCursor(0, 32);

  display.print("Smoke: ");

  display.print(fireSystem.smokeLevel);

  display.println(" %");

 

  // Flame

  display.setCursor(0, 42);

  display.print("Flame: ");

  display.print(fireSystem.flameLevel);

  display.println(" %");

 

  // Systems status

  display.setCursor(0, 52);

  if (fireSystem.sprinklerActive) display.print("SPRNKLR ");

  if (fireSystem.exhaustFanActive) display.print("FAN ");

  if (fireSystem.alarmActive) display.print("ALARM");

 

  display.display();

}

void sendAlert() {

  fireSystem.alertCount++;

  fireSystem.lastAlert = millis();

 

  Serial.println("\n╔══════════════════════════════════════╗");

  Serial.println("║     🚨 EMERGENCY ALERT SENT 🚨      ║");

  Serial.println("╠══════════════════════════════════════╣");

  Serial.print("║ Location: ");

  Serial.println(fireSystem.location);

  Serial.print("║ Level: ");

  Serial.println(getAlertLevelName(fireSystem.alertLevel));

  Serial.print("║ Temperature: ");

  Serial.print(fireSystem.temperature, 1);

  Serial.println(" °C");

  Serial.print("║ Smoke: ");

  Serial.print(fireSystem.smokeLevel);

  Serial.println(" %");

  Serial.println("║                                      ║");

  Serial.println("║ ✉️  Email sent to: admin@fire.dept  ║");

  Serial.println("║ 📱 SMS sent to: Fire Department     ║");

  Serial.println("║ 🔔 Push notification sent          ║");

  Serial.println("╚══════════════════════════════════════╝\n");

}

void logAlert() {

  alertHistory[historyIndex].timestamp = String(millis() / 1000) + "s";

  alertHistory[historyIndex].level = getAlertLevelName(fireSystem.alertLevel);

  alertHistory[historyIndex].temp = fireSystem.temperature;

  alertHistory[historyIndex].smoke = fireSystem.smokeLevel;

  alertHistory[historyIndex].flame = fireSystem.flameLevel;

 

  historyIndex = (historyIndex + 1) % 10;

}

String getAlertLevelName(AlertLevel level) {

  switch(level) {

    case SAFE: return "SAFE";

    case WARNING: return "WARNING";

    case DANGER: return "DANGER";

    case CRITICAL: return "CRITICAL";

    default: return "UNKNOWN";

  }

}

String getAlertColor(AlertLevel level) {

  switch(level) {

    case SAFE: return "#4CAF50";

    case WARNING: return "#2196F3";

    case DANGER: return "#FF9800";

    case CRITICAL: return "#F44336";

    default: return "#999";

  }

}

void playStartupTone() {

  tone(BUZZER_PIN, 1000, 100);

  delay(150);

  tone(BUZZER_PIN, 1500, 100);

  delay(150);

  tone(BUZZER_PIN, 2000, 100);

}

// Web Server Handlers

void handleRoot() {

  String html = "<!DOCTYPE html><html><head>";

  html += "<meta name='viewport' content='width=device-width,initial-scale=1'>";

  html += "<meta http-equiv='refresh' content='2'>";

  html += "<title>Fire Detection System</title>";

  html += "<style>";

  html += "body{margin:0;font-family:Arial;background:#1a1a1a;color:#fff;padding:20px}";

  html += ".container{max-width:1200px;margin:0 auto}";

  html += "h1{text-align:center;font-size:2.5em;margin-bottom:5px}";

  html += ".subtitle{text-align:center;opacity:0.7;margin-bottom:30px}";

  html += ".alert-banner{padding:20px;border-radius:10px;margin-bottom:20px;text-align:center;font-size:1.5em;font-weight:bold;animation:pulse 2s infinite}";

  html += "@keyframes pulse{0%,100%{opacity:1}50%{opacity:0.7}}";

  html += ".grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(250px,1fr));gap:20px;margin-bottom:20px}";

  html += ".card{background:rgba(255,255,255,0.1);padding:20px;border-radius:10px;border:2px solid rgba(255,255,255,0.2)}";

  html += ".sensor-value{font-size:2.5em;font-weight:bold;margin:10px 0}";

  html += ".sensor-label{opacity:0.7;font-size:0.9em}";

  html += ".progress{background:rgba(255,255,255,0.2);height:20px;border-radius:10px;overflow:hidden;margin:10px 0}";

  html += ".progress-bar{height:100%;transition:width 0.3s}";

  html += ".status-indicator{display:inline-block;width:20px;height:20px;border-radius:50%;margin-right:10px}";

  html += ".btn{padding:15px 30px;border:none;border-radius:8px;cursor:pointer;font-size:1em;margin:5px;color:#fff;text-decoration:none;display:inline-block}";

  html += ".btn-danger{background:#f44336}";

  html += ".btn-primary{background:#2196F3}";

  html += ".systems{background:rgba(255,255,255,0.05);padding:20px;border-radius:10px;margin-top:20px}";

  html += ".system-item{display:flex;justify-content:space-between;align-items:center;padding:10px;border-bottom:1px solid rgba(255,255,255,0.1)}";

  html += "</style></head><body>";

  html += "<div class='container'>";

 

  html += "<h1>🚨 Fire Detection System</h1>";

  html += "<div class='subtitle'>" + fireSystem.location + "</div>";

 

  // Alert Banner

  String alertColor = getAlertColor(fireSystem.alertLevel);

  html += "<div class='alert-banner' style='background:" + alertColor + "'>";

  html += "⚠️ " + getAlertLevelName(fireSystem.alertLevel);

  if (fireSystem.alertLevel >= DANGER) {

    html += " - EVACUATE IMMEDIATELY!";

  }

  html += "</div>";

 

  // Sensor Readings

  html += "<div class='grid'>";

 

  // Temperature

  html += "<div class='card'>";

  html += "<div class='sensor-label'>🌡️ Temperature</div>";

  html += "<div class='sensor-value'>" + String(fireSystem.temperature, 1) + "°C</div>";

  int tempPercent = map(constrain(fireSystem.temperature, 0, 60), 0, 60, 0, 100);

  String tempColor = fireSystem.temperature >= TEMP_CRITICAL ? "#F44336" :

                     fireSystem.temperature >= TEMP_DANGER ? "#FF9800" : "#4CAF50";

  html += "<div class='progress'><div class='progress-bar' style='width:" + String(tempPercent) + "%;background:" + tempColor + "'></div></div>";

  html += "</div>";

 

  // Smoke

  html += "<div class='card'>";

  html += "<div class='sensor-label'>💨 Smoke Level</div>";

  html += "<div class='sensor-value'>" + String(fireSystem.smokeLevel) + "%</div>";

  String smokeColor = fireSystem.smokeLevel >= SMOKE_CRITICAL ? "#F44336" :

                      fireSystem.smokeLevel >= SMOKE_DANGER ? "#FF9800" : "#4CAF50";

  html += "<div class='progress'><div class='progress-bar' style='width:" + String(fireSystem.smokeLevel) + "%;background:" + smokeColor + "'></div></div>";

  html += "</div>";

 

  // Flame

  html += "<div class='card'>";

  html += "<div class='sensor-label'>🔥 Flame Detection</div>";

  html += "<div class='sensor-value'>" + String(fireSystem.flameLevel) + "%</div>";

  String flameColor = fireSystem.flameLevel >= FLAME_THRESHOLD ? "#F44336" : "#4CAF50";

  html += "<div class='progress'><div class='progress-bar' style='width:" + String(fireSystem.flameLevel) + "%;background:" + flameColor + "'></div></div>";

  html += "</div>";

 

  // Humidity

  html += "<div class='card'>";

  html += "<div class='sensor-label'>💧 Humidity</div>";

  html += "<div class='sensor-value'>" + String(fireSystem.humidity, 1) + "%</div>";

  html += "</div>";

 

  html += "</div>"; // End grid

 

  // Safety Systems Status

  html += "<div class='systems'>";

  html += "<h3>Safety Systems</h3>";

 

  html += "<div class='system-item'>";

  html += "<span><span class='status-indicator' style='background:" + String(fireSystem.sprinklerActive ? "#4CAF50" : "#666") + "'></span>🚿 Sprinkler System</span>";

  html += "<span>" + String(fireSystem.sprinklerActive ? "ACTIVE" : "Standby") + "</span>";

  html += "</div>";

 

  html += "<div class='system-item'>";

  html += "<span><span class='status-indicator' style='background:" + String(fireSystem.exhaustFanActive ? "#4CAF50" : "#666") + "'></span>💨 Exhaust Fan</span>";

  html += "<span>" + String(fireSystem.exhaustFanActive ? "ACTIVE" : "Standby") + "</span>";

  html += "</div>";

 

  html += "<div class='system-item'>";

  html += "<span><span class='status-indicator' style='background:" + String(fireSystem.alarmActive ? "#F44336" : "#666") + "'></span>🔔 Alarm System</span>";

  html += "<span>" + String(fireSystem.alarmActive ? "SOUNDING" : "Silent") + "</span>";

  html += "</div>";

 

  html += "</div>";

 

  // Controls

  html += "<div style='text-align:center;margin-top:30px'>";

  html += "<a href='/test' class='btn btn-danger'>Test Alarm</a>";

  html += "<a href='/silence' class='btn btn-primary'>Silence Alarm</a>";

  html += "<a href='/reset' class='btn btn-primary'>Reset System</a>";

  html += "</div>";

 

  html += "<div style='text-align:center;margin-top:20px;opacity:0.5;font-size:0.9em'>";

  html += "Alerts: " + String(fireSystem.alertCount) + " | ";

  html += "Uptime: " + String(millis()/1000) + "s | ";

  html += "IP: " + WiFi.localIP().toString();

  html += "</div>";

 

  html += "</div></body></html>";

 

  server.send(200, "text/html", html);

}

void handleStatus() {

  String json = "{";

  json += "\"temperature\":" + String(fireSystem.temperature, 2) + ",";

  json += "\"humidity\":" + String(fireSystem.humidity, 2) + ",";

  json += "\"smoke\":" + String(fireSystem.smokeLevel) + ",";

  json += "\"flame\":" + String(fireSystem.flameLevel) + ",";

  json += "\"alertLevel\":\"" + getAlertLevelName(fireSystem.alertLevel) + "\",";

  json += "\"sprinkler\":" + String(fireSystem.sprinklerActive ? "true" : "false") + ",";

  json += "\"exhaustFan\":" + String(fireSystem.exhaustFanActive ? "true" : "false") + ",";

  json += "\"alarm\":" + String(fireSystem.alarmActive ? "true" : "false") + ",";

  json += "\"alertCount\":" + String(fireSystem.alertCount);

  json += "}";

 

  server.send(200, "application/json", json);

}

void handleHistory() {

  String json = "[";

  for (int i = 0; i < 10; i++) {

    if (alertHistory[i].timestamp != "") {

      if (i > 0) json += ",";

      json += "{";

      json += "\"time\":\"" + alertHistory[i].timestamp + "\",";

      json += "\"level\":\"" + alertHistory[i].level + "\",";

      json += "\"temp\":" + String(alertHistory[i].temp, 1) + ",";

      json += "\"smoke\":" + String(alertHistory[i].smoke) + ",";

      json += "\"flame\":" + String(alertHistory[i].flame);

      json += "}";

    }

  }

  json += "]";

 

  server.send(200, "application/json", json);

}

void handleReset() {

  fireSystem.alertCount = 0;

  fireSystem.alarmActive = false;

  historyIndex = 0;

  for (int i = 0; i < 10; i++) {

    alertHistory[i].timestamp = "";

  }

 

  Serial.println("✓ System reset");

  server.sendHeader("Location", "/");

  server.send(303);

}

void handleTest() {

  Serial.println("🧪 Running alarm test...");

  for (int i = 0; i < 3; i++) {

    tone(BUZZER_PIN, 2000, 200);

    delay(300);

  }

 

  server.sendHeader("Location", "/");

  server.send(303);

}

void handleSilence() {

  fireSystem.alarmActive = false;

  digitalWrite(BUZZER_PIN, LOW);

  Serial.println("🔇 Alarm silenced manually");

 

  server.sendHeader("Location", "/");

  server.send(303);

}

Applications

• Home safety
• Industrial facilities
• Warehouses
• Commercial buildings

Difficulty Level

Intermediate to Advanced

Amazing Features:

Triple Sensor Detection:

•  DHT22 - Temperature monitoring (triggers at 35°C, 45°C, 55°C)
•  MQ-2 Smoke Sensor - Gas/smoke detection (0-100%)
•  Flame Sensor - Infrared flame detection

4-Level Alert System:

SAFE → Green LED, No alarm

WARNING  → Blue LED, No alarm  
DANGER   → Red LED + Medium beeps
CRITICAL → Red flashing + Fast beeps

Automatic Safety Response:

•  Auto-Sprinkler - Activates at CRITICAL level
•  Exhaust Fan - Turns on when smoke > 30%
•  Smart Alarm - Different beep patterns per level
•  Emergency Alerts - Simulated SMS/Email notifications

Beautiful Web Dashboard:

•  Dark theme with color-coded alerts
•  Progress bars for all sensors
•  Auto-refresh every 2 seconds
•  Mobile responsive design
•  Remote controls (Test, Silence, Reset)

 How to Test:

Simulate a Fire:

1. Start with Normal Conditions:
   • Green LED = SAFE
   • No alarm
   • All systems standby
2. Increase Temperature:
   • Click DHT22, drag to 40°C
   • Blue LED lights up (WARNING)
   • Still no alarm
3. Add Smoke:
   • Rotate "Smoke Sensor" to 60%
   • Red LED lights up (DANGER)
   • Alarm starts beeping!
   •  Exhaust fan turns ON
4. Detect Flames:
   • Rotate "Flame Sensor" to 50%
   • Red LED flashes rapidly (CRITICAL)
   • Alarm beeps continuously
   • Sprinkler activates!
   • Emergency alerts sent!

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Conclusion: Start Your ESP32 IoT Journey Today

The ESP32 microcontroller opens up endless possibilities for IoT innovation. These 15 projects cover a wide spectrum of applications, from simple home automation to complex industrial monitoring systems.