<![CDATA[Indoor air quality is an important factor affecting human health because most daily activities are carried out in enclosed environments. Conventional air quality monitoring systems generally focus on monitoring functions without integrating automatic air purification and comprehensive historical data visualization. This study aims to design and implement an Internet of Things (IoT)-based air purifier using ESP32, MQ-9 and MQ-135 gas sensors, MQTT, Node-RED, InfluxDB, and Grafana. The proposed system monitors indoor air quality in real time, automatically controls DC fan speed based on air quality conditions, provides local notifications through RGB LEDs and a buzzer, stores sensor data in a time-series database, and visualizes historical data through a web-based dashboard. System testing was conducted using several pollutant sources, including paper combustion smoke, air freshener, and perfume under both open and enclosed conditions. The results indicate that the system successfully detected changes in air quality, automatically adjusted fan speed, activated visual and audible indicators according to predefined thresholds, and transmitted sensor data to the monitoring dashboard in real time. These results demonstrate that the proposed system can effectively integrate real-time monitoring, automatic air purification, historical data storage, and user notification within a single IoT-based platform.]]>
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