Smart Air Quality Monitoring System using Arduino

The Smart Air Quality Monitoring System uses an Arduino Nano as the central processing unit to continuously track environmental conditions. At the heart of the sensing subsystem is the MQ135 gas sensor, which is sensitive to a variety of harmful gases and pollutants in the air, such as smoke, carbon dioxide, and various volatile organic compounds. As the concentration of these gases changes in the surrounding environment, the sensor produces a corresponding analog voltage output. This analog signal is routed into one of the analog input pins on the Arduino Nano, where the built-in analog-to-digital converter transforms the continuous voltage into a readable digital value. The Arduino Nano's microcontroller runs a programmed sketch that constantly reads this data and evaluates it against a predefined safety threshold. To keep the user informed, the system features a 16×2 LCD display connected via the I2C communication protocol, which minimizes the number of required wiring pins by using only the serial data (SDA) and serial clock (SCL) lines to output live air quality status updates. If the sensor reading exceeds the safe threshold limit, the Arduino immediately triggers an active buzzer connected to one of its digital output pins, emitting an audible alarm to alert anyone nearby of degraded air quality conditions. The entire circuit is powered via a USB cable or an optional 9V battery distributed through a breadboard using jumper wires.