Optical portable instrument for the determination of CO2 in indoor environments

Abstract

A portable device based on a colorimetric sensor to determine the atmospheric level of CO 2 gas is presented in this work. The system is based on a low-cost, low-power System on a Chip (SoC) microcontroller with integrated Wi-Fi. A user-friendly application was developed to monitor and log the CO 2 measurements when the system is connected to a Wi-Fi network. The sensing membrane is directly deposited on the surface of the colour detector, thus reducing the complexity of the system. This sensing membrane is formed by a pH indicator α-naphtholphthalein, tetramethylammonium hydroxide pentahydrate, 1-ethyl-3-methylimidazolium tetrafluoroborate, Tween 20 and hydroxypropyl methylcellulose as the hydrophilic polymer. The system has been fully characterized, obtaining response and recovery times of 1.3 and 2.5 s, respectively, a limit of detection of 51 ppm, and an average resolution of 6.3 ppm. This portable device was applied for the in-situ determination of CO 2 gas in the atmosphere inside classrooms in several secondary schools. The measurements were taken during complete workdays and the results were statistically compared with the same measurements taken using a commercially available non-dispersive infra-red (NDIR) device. No significant statistical differences were found between the results obtained using both devices. A complete statistical treatment of the measurements made with the proposed portable device was carried out. The obtained results show that the *Revised Manuscript (clean copy) Click here to view linked References 2 concentration of CO gas in some schools was higher than the desired concentration, with regard to influencing the student's health, safety, productivity and comfort. This demonstrates the need to control this parameter to ensure appropriate indoor environmental quality (IEQ).

Near Infrared Sensor to Determine Carbon Dioxide Gas Based on Ionic Liquid

“…The dependence of the relative humidity of the sensing membrane at room temperature (22 ± 1 • C) was studied, obtaining the calibration function at relative humidities between 10% and 100% and observing a reduction in sensitivity with as the % RH increases (Figure 2). The experiments assays were carried out at a constant room temperature, 22 ± 1 • C, in all cases, although there is a known decrease in sensitivity as the temperature increases [42]. This fact occurs owing to the opposite dependence of CO 2 solubility in the pH indicator membrane on the temperature [43].…”

“…For that reason, the detection limit, LOD, was calculated from the raw exponential experimental data by using the first three points (Figure 3 insert), which can be adjusted to a straight line, I/I100 = 0.0051[% CO2] + 0.856; R 2 = 0.989 [49], using (LOD = t0N − 3s0), where t0N is the 1 °C) was studied, obtaining the calibration function at relative humidities between 10% and 100% and observing a reduction in sensitivity with as the % RH increases (Figure 2). The experiments assays were carried out at a constant room temperature, 22 ± 1 °C, in all cases, although there is a known decrease in sensitivity as the temperature increases [42]. This fact occurs owing to the opposite dependence of CO2 solubility in the pH indicator membrane on the temperature [43].…”

Smart Wireless CO2 Sensor Node for IoT Based Strategic Monitoring Tool of The Risk of The Indoor SARS-CoV-2 Airborne Transmission

“…Most of these sensor systems, as mentioned above, are multiparameter air-quality sensor systems. Moreover, IAQ monitoring devices that are available in the market mentioned in [31][32][33][34] also tend to consume relatively high power, are relatively large devices, and are fairly expensive; therefore, they do not meet the requirement for indoor-monitoring applications. The sensor node should have low-power consumption for long-period operation, be easily installed in limited space indoors, and have low-cost development, as well as being easily utilized and accessed.…”

Monitoreo del voltaje de una placa solar y calidad luminosa usando Internet de las Cosas

“…Se ha documentado que la plataforma myDevices Cayenne provee el soporte necesario para desarrollar aplicaciones robustas de IoT con placas de libre acceso como Arduino, ESP8266 y varias versiones de Raspberry Pi y LoRa (Fernández et al, 2020).…”