This application will help you to monitor your MQ2 gas sensor data with Bluetooth. This is a very simple application that uses an MQ2 gas sensor to monitor and analyze the smoke or gas levels around you. The circuit contains an Arduino microcontroller, an hc05 Bluetooth module, and an MQ2 gas sensor. The MQ2 sensor's analog output pin is connected to the microcontroller's analog pin, and the sensor value is sent to the app through Bluetooth. Then it will be displayed in the app in a big circular progress bar and a line chart. The MQ2 sensor normally produces a value between 500 and 600 in clean air. When smoke or combustible gas is detected in its environment, the sensor produces readings greater than 800.You can set the threshold value in the app as well as the Arduino code to receive notifications based on the sensitivity of the sensor you used.