IoT-Based Low-Cost Intelligent Air-Quality Monitoring and Self-Calibrated Autonomous Purification System

The main contributions of this work are summarized as
follows:
• A low-cost ESP32-S3-based system is developed for
air quality monitoring, AQI calculation, sensor-health
tracking, and automatic purification.
• A simple, equation-based processing method is used
for data preprocessing, anomaly detection, and sensor
self-calibration before the AQI is calculated.
• The current AQI is calculated using the standard AQI
equation, supported by a lightweight, equation-based
Sensor Health Indicator (SHI) that continuously tracks
per-sensor reliability.
• A simple, AQI-based purification control scheme is
developed, where the purifier is automatically turned on
or off according to a dedicated control AQI, while sensors
flagged as unreliable by the SHI are excluded from that
control AQI’s dominant-pollutant computation; the AQI
reported for remote visualization is unaffected and always
reflects all six sensor channels.
• A solar-first power system with a solar panel, MPPT,
battery management, and DC regulation is integrated to
support the ESP32-S3 and the purification unit.
• The system supports multiple pollutant measurements
and local edge operation, while ThingSpeak provides
remote monitoring of air quality and system status.