# System for Indoor Comfort and Health Monitoring Tested in Office Building Environment
## 3 Methodology of the Proposed IoT System Development
### Solution of the Smart IoT System for Monitoring of Indoor Comfort and Health  
The selection of the relevant sensors for the solution development begins with the establishment of the physical parameters that are considered important for monitoring. Based on the main physical parameters to be measured related to the environmental quality and comfort, the sensors and other components of the IoT system were selected. The components as well as their performance are shown in Table 6. \begin{table}
\begin{tabular}{c c c} \hline
**No.** & **Sensor** & **Specifications** \\ \hline \multirow{6}{*}{1} & NDIR CO\({}_{2}\), temperature and humidity sensor & Manufacturer series: SCD30; \\  & module & Supply voltage: 3.3 V... 5.5 V; \\  & & Operating temperature: 0–50 \({}^{\circ}\)C; \\  & & Supply current: 19 mA; \\  & & CO\({}_{2}\) measuring range: 0... 10,000 rpm; \\  & & Temperature measuring range: \(-\)40–120 \({}^{\circ}\)C; \\  & & Humidity measuring range: 0-1000* RH; \\  & & Accuracy: \(\pm\)(30 ppm + 3\%). \\ \hline \multirow{6}{*}{2} & Formaldehyde, temperature and humidity sensor & \\  & module & Manufacturer series: SFA30-D-T Sensiriom; \\  & & Working temperature: 0... 450 \({}^{\circ}\)C; \\  & & Supply voltage: 3.3 V... 5 V; \\  & & Measurement accuracy: (50 \(\pm\) 5\% RH, (25 \(\pm\) 3) \({}^{\circ}\)C, formaldehyde concentration 0... \\  & & 200 ppb; \\ \hline \multirow{6}{*}{3} & CO\({}_{2}\) sensor module and & \\  & volatile organic compounds & Manufacturer series: MICS-VZ-89 TE; \\  & & Supply voltage: 3.3 V DC; \\  & & Working temperature: 0”... 450 \({}^{\circ}\)C; \\  & & Monitoring Range: 400-2000 ppm equivalent CO\({}_{2}\); \\  & & Monitoring Range: 0-1000 ppb isovolylene equivalent TVOC; \\  & & Updated output frequency: 1 Hz; \\  & & Maximum number of particles: 2000 ppm; \\ \hline \multirow{6}{*}{4} & Dust particle sensor & Manufacturer series: PMS5003; \\  & Dust particle measuring range: 0.3... 1.0 \(\mu\)m; 1.0... 2.5 \(\mu\)m; 2.5 \(\mu\)m; 10 \(\mu\)m; \\  & Measurement efficiency: 50\% for 0.3 \(\mu\)m particles; 98\% for particles \(\geq\)0.5 \(\mu\)m; \\  & Working temperature: 10 – 460 \({}^{\circ}\)C; \\  & & Supply voltage: 45 V... 5.5 V; \\  & & PM1.0/PM2.5 \(<\)50 ug/m\({}^{3}\); \(\pm\)5 ug/m\({}^{3}\); 50–1000 ug/m\({}^{3}\); \(\pm\)10\%; \\  & PM10: \(\leq\)100 ug/m\({}^{3}\): \(\pm\)15 ug/m\({}^{3}\), 100–1000 ug/m\({}^{3}\): \(\pm\)15\% Reading. \\ \hline \end{tabular}
\end{table} 
Table 6: Components of the smart IoT system for monitoring of indoor comfort and health. Table 6 highlights the sensors suitable for implementing the experimental model and their technical specifications. Subsequently, several sensors measuring the same parameters were selected for the purpose of validating the measurement process of the proposed IoT system. The Sensirion SCD30 (CO2, humidity, and temperature) sensor module was set to use I2C communication. For CO2 measurement, the sensor uses NDIR technology. CMOSens(r) technology for IR detection enables the highest-accuracy carbon dioxide measurements at a competitive price and has dual-channel detection for superior stability. Ambient humidity and temperature were measured by Sensirion's algorithm expertise through modelling and compensating the external heat sources without the need for any additional components using a temperature and humidity sensor integrated into the very same module. The Sensirion SFA30 formaldehyde sensor module for HVAC and indoor air quality applications was also set to use I2C communication. The sensor is based on electrochemical sensing technology optimized for the lowest false alarm rates. The MiCS-VZ-89 TE is an integrated sensor board for indoor air quality monitoring and combines state-of-the-art MOS sensor technology (semiconductor gas sensor, detecting a wide range of VOCs) with intelligent detection algorithms to monitor total volatile organic compounds and CO2 equivalent variations in confined spaces. The sensor was set to send data via I2C communication.