Complete tutorial : https://help.sinric.pro/pages/tutorials/custom-device-types/alcohol-sensor/MQ-3.html

GasSensor.h

#ifndef _GASSENSOR_H_
#define _GASSENSOR_H_

#include <SinricProDevice.h>
#include <Capabilities/ModeController.h>
#include <Capabilities/PushNotification.h>

class GasSensor 
: public SinricProDevice
, public ModeController<GasSensor>
, public PushNotification<GasSensor> {
  friend class ModeController<GasSensor>;
  friend class PushNotification<GasSensor>;
public:
  GasSensor(const String &deviceId) : SinricProDevice(deviceId, "GasSensor") {};
};

#endif

sinricpro-mq4-sensor.ino

// Uncomment the following line to enable serial debug output
//#define ENABLE_DEBUG

#ifdef ENABLE_DEBUG
  #define DEBUG_ESP_PORT Serial
  #define NODEBUG_WEBSOCKETS
  #define NDEBUG
#endif

#include <Arduino.h>
#ifdef ESP8266
  #include <ESP8266WiFi.h>
#endif
#ifdef ESP32
  #include <WiFi.h>
#endif

#include <SinricPro.h>
#include "GasSensor.h"

#define WIFI_SSID         ""   // Your WiFI SSID name 
#define WIFI_PASS         ""   // Your WiFi Password.

#define APP_KEY           ""   // Should look like "de0bxxxx-1x3x-4x3x-ax2x-5dabxxxxxxxx" (Get it from Portal -> Secrets)
#define APP_SECRET        ""   // Should look like "5f36xxxx-x3x7-4x3x-xexe-e86724a9xxxx-4c4axxxx-3x3x-x5xe-x9x3-333d65xxxxxx" (Get it from Portal -> Secrets)
#define DEVICE_ID         ""   // Should look like "5dc1564130xxxxxxxxxxxxxx" (Get it from Portal -> Devices)

#define BAUD_RATE         115200              // Change baudrate to your need (used for serial monitor)
#define EVENT_WAIT_TIME   60000               // send event every 60 seconds

#if defined(ESP8266)
  const int adcPin = A0;  
#elif defined(ESP32) 
  const int adcPin = 34;  
#elif defined(ARDUINO_ARCH_RP2040)
  const int adcPin = 26;  
#endif

#define BAUD_RATE         115200              // Change baudrate to your need (used for serial monitor)
#define EVENT_WAIT_TIME   60000               // send event every 60 seconds

const int GAS_DETECTED_THRESHOLD = 850;       // Change accordingly

GasSensor &gasSensor = SinricPro[DEVICE_ID];
int sensorVal;
String sensorState = "";
String lastSensorState = "";

// ModeController
void updateMode(String mode) {
  gasSensor.sendModeEvent("modeInstance1", mode, "PHYSICAL_INTERACTION");
}

// PushNotificationController
void sendPushNotification(String notification) {
  gasSensor.sendPushNotification(notification);
}

void setupSinricPro() {
  SinricPro.onConnected([]{ Serial.printf("[SinricPro]: Connected\r\n"); });
  SinricPro.onDisconnected([]{ Serial.printf("[SinricPro]: Disconnected\r\n"); });
  SinricPro.begin(APP_KEY, APP_SECRET);
}

 void handleM3Sensor() {
  if (SinricPro.isConnected() == false) {
    return; 
  }

  static unsigned long last_millis;
  unsigned long        current_millis = millis();
  if (last_millis && current_millis - last_millis < EVENT_WAIT_TIME) return;
  last_millis = current_millis;
    
  sensorVal = analogRead(adcPin);
  Serial.printf("Sensor value: %d\r\n", sensorVal); 

  if (sensorVal > GAS_DETECTED_THRESHOLD) { // "Detected" or "Not-Detected" (from ModeController mode values)
    sensorState = "Detected"; 
  } else {
    sensorState = "Not-Detected";
  }

  if(sensorState != lastSensorState) {
    /* update server with "detected" / "Not-Detected" status */
    updateMode(sensorState); 

    /* send a push notification when gas detected */
    if(sensorState == "Detected") {
      sendPushNotification("Gas Detected!!!");
    }    
  } 

  lastSensorState = sensorState;  // save to compare next time.
}

void setupWiFi() {
  #if defined(ESP8266)
    WiFi.setSleepMode(WIFI_NONE_SLEEP); 
    WiFi.setAutoReconnect(true);
  #elif defined(ESP32)
    WiFi.setSleep(false); 
    WiFi.setAutoReconnect(true);
  #endif

  WiFi.begin(SSID, PASS);
  Serial.printf("[WiFi]: Connecting to %s", SSID);
  while (WiFi.status() != WL_CONNECTED) {
    Serial.printf(".");
    delay(250);
  }
  Serial.printf("connected\r\n");
}

void setup() {
  Serial.begin(BAUD_RATE);
  setupWiFi();
  setupSinricPro();
}

/********
 * Loop *
 ********/

void loop() {
  handleM3Sensor();
  SinricPro.handle();
}