Implementation of a Low-Cost IoT Indoor Air Quality Monitor in Dynamic Public Environments

We implement an affordable Internet of Things (IoT) device for evaluating indoor air quality (IAQ) in dynamically changing public environments, such as transportation buses and shopping centers in San Luis Potosi, Mexico. An ESP32 microcontroller integrates the monitor with a DS18B20 temperature sensor and a PMS5003 particulate matter (PM) sensor to measure PM2.5 and PM10. The monitor uses the fifth generation mobile network to transmit this information to the IoT platform ThingSpeak for storage and further analysis. Over six days, we measured three bus routes during the morning and afternoon and four shopping centers in the afternoon, as experienced by an ordinary user. Results show that PM2.5 and PM10 levels can achieve 116 and 121 μg/m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>, respectively, which are dangerous for human health, thus demonstrating the potential of communication technologies and low-cost IoT devices for implementing IAQ monitoring in resource-constrained scenarios, highlighting the need for adequate ventilation policies and compliance in such dynamic public spaces.