IoT-MQTT Architecture for Indoor Air Quality Monitoring
Keywords:
Air quality, indoor spaces, IoT, IAQI, MQTT.Abstract
Indoor Air Quality (IAQ) is a crucial factor in mitigating respiratory diseases, as individuals spend up to 90% of their time indoors, especially in academic spaces where occupants remain for extended periods. However, traditional IAQ monitoring systems commonly rely on proprietary commercial ecosystems, restricting accessibility, interoperability, and adaptability. This study presents an IoT-MQTT architecture based on open-access technologies for near-real-time IAQ monitoring, which considers parameters such as carbon dioxide (CO2), total volatile organic compounds (TVOC), temperature, and relative humidity. It was developed through a four-phase methodology encompassing technological research and surveillance, design, development, and testing. The system integrates three sensing nodes built upon the ESP32 microcontroller with CCS811 and DHT22 sensors, embedding a custom linear offset compensation algorithm within its firmware for thermo-hygrometric variables. Technical and operational validation testing of the architecture was conducted in a 60.48 m² university classroom over five consecutive days, utilizing a 10-second sampling interval to transmit data to a broker hosted on ThingSpeak, alongside local replication on a Raspberry Pi with persistence in Supabase. The system successfully detected microclimatic variations linked to occupancy and ventilation, revealing peaks up to approximately 1300 ppm of CO2 and 220 ppb of TVOC under high occupancy and limited air exchange conditions. The results demonstrate the feasibility, stability, and replicability of the architecture based on affordable open-access technologies, establishing a solid architectural foundation for the future implementation of automated environmental ventilation control strategies in academic environments.
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