A multi function and cost effective sensor network system development for indoor air quality monitoring applications. Validation procedure and experimental tests in a school classroom

Indoor air quality (IAQ) in school buildings is a fundamental requirement that influences students' health and academic productivity. This paper employs the Internet of Things (IoT) technology to develop a cost-effective and multi-function sensor network system that monitors indoor air parameters such as temperature, relative humidity (RH), carbon dioxide equivalent (CO2eq), and total volatile organic compounds (TVOC). In addition, the sensor collects occupants'feedbacks through a user-friendly command board and makes it possible to estimate the ventilation efficiency of a room, thanks to the connection with additional sensors capable to monitor the opening and closing patterns of windows and doors. An experimental procedure was conducted in a school classroom to test the system‘s performance, present the methodology for data reading, and evaluate indoor air quality. The system has demonstrated its efficacy in raising awareness among users about indoor air quality and has proven to be an effective tool for qualitative and quantitative control of natural ventilation. These systems present new opportunities for the aggregation of multi-source data and for creating pollution distribution maps in the future, leveraging the system's low cost and wide reach. The main results showed low user sensitivity to air quality and TVOC content, while a better understanding of temperature and CO2 levels was observed, but without a complete understanding of the actual measurement data. However, simultaneous opening of windows and doors can provide the recommended ventilation rate for health (4 L/s per person) and decrease all concentrations below 1500 ppm. The device developed and the tested procedure can therefore contribute to systemic monitoring of the phenomenon, predicting patterns of opening and closing of windows and improving ventilation management in spaces. The paper also contains a series of electrical specifications and material selection criteria to support the construction of the device.