Air Quality Assessment Based on a Smart Locally CO2 Monitoring System with Validation by a Reference Instrument

Abstract

This article deals with the development and implementation of a low-cost smart air quality monitoring device. The study aims to develop a simple, efficient, and cheap device for real-time monitoring of Carbon dioxide (CO₂) concentration and atmospheric parameters such as temperature (T) and relative humidity (RH). The realized device consists of sensors, a data storage system, a programmable card, and wireless modules for Internet of Things (IoT). It is designed for indoor and outdoor air quality monitoring. Wireless communication between the device and the control PC is ensured by the ZigBee protocol. The MH-Z14A sensor was calibrated according to the manufacturer’s recommendations and then experimentally in the laboratory. A calculation of the CO₂ regression line for the devices using the least squares method gave R² = 0.6889. The slope test using the Student method at a significant coefficient of 1% threshold and 19 degrees of freedom gave t(1%; 19) = 2.539. This illustrates that the result obtained by the realized device has less than a 1% chance of being obtained at random. An investigation was carried out to assess air quality because following the proliferation of pollutants, the normal concentration of atmospheric CO₂ (400 ppm) has considerably changed. Thus, the data processed are outdoor concentrations collected in November 2022 in some localities of the Adamawa Region, Cameroon. The average values of CO₂ concentration measured in four subdivisions are 497.30 ± 11.32 ppm in Ngaoundéré 1, 481.83 ± 14.90 ppm in Ngaoundéré 2, 568.63 ± 25.03 ppm in Martap and, 624.14 ± 3.96 ppm in Minim. Martap and Minim are among the most important bauxite deposits in the world. These CO₂ values higher than the normal atmospheric concentration indicate a moderate Air Quality Index (AQI) in these cities during the measurement period. The designed device is inexpensive, reliable, and appropriate for air quality monitoring.