MQ2 gas sensor detects smoke and leakage of combustible gas Methane, Butane, LPG etc. ESP8266 reads the sensor data and push the same to ThingSpeak (IoT analytics platform) using MQTT. If the gas concentration exceeds the preset threshold value (calibrated), ESP8266 triggers the alarm (buzzer) with a flashing red LED. On the other hand, ThingSpeak "React"s and initiates the action "ThingHTTP" to call Twilio (Cloud communications platform) API to send SMS notification. ThingSpeak also provides option to visualize (barchart, gauge) the data pushed by ESP8266.