## 5 System Performance
### Multi-Sensor Validation  
To validate the multi-sensor operations, a one-day measurement campaign was conducted in an office space with the setup shown in Figure 12. Alongside the developed multi-sensor, a commercially available IEQ monitoring device [33] was positioned as closely as possible to the multi-sensor to ensure collection of comparable data. Additionally, measurements from reference instruments situated in the same room were obtained for comparison purposes. More precisely, the reference for relative humidity was [60], ref. [61] for illuminance, ref. [62] for sound pressure level, and ref. [63] for carbon dioxide. The results of the measurement campaign are shown in Figure 13 for temperature, relative humidity, illuminance, and sound pressure level. Solid lines refer to data collected by the developed multi-sensor, dashed lines correspond to data from the commercial device, and dashed-dotted lines refer to measurements from the reference instruments. As far as data collected by PROMET&O are concerned, they refer to the averages at report time for temperature, relative humidity, and illuminance. Conversely, sound pressure level collected by the multi-sensor refers to equivalent sound pressure level evaluated over a 500 ms time window. Regarding temperature, the measurements from the PROMET&O and the commercial device exhibit good agreement, whereas thermocouple used as reference resulted in a measurement 2 \({}^{\circ}\)C lower. Similarly, illuminance showed consistent agreement among the various devices. Concerning relative humidity, the PROMET&O device overestimated the measurement by 5% compared to the other two devices. Lastly, the sound pressure level, weighted in accordance with the A-curve as reported in (4), was compared between the developed multi-sensor and the sound level meter. These results are in good agreement, with a minor error of a few decibels. Regarding IAQ, the measurements of carbon dioxide, TVOCs, PM 2.5, and PM 10 for the setup shown in Figure 12 are reported in Figure 14, where solid, dashed, and dashed-dotted lines represent data collected by PROMET&O, the commercial device, and the reference instruments, respectively. More precisely, solid lines refer to the average value of data collected by the respective sensor over a report time window. For the other air quality sensors included in the developed multi-sensor device, their respective gas concentrations  
Figure 12: Experimental setup with the PROMET&O multi-sensor, a commercial device, and some reference instruments in an office. Figure 13: Temperature, relative humidity, illuminance, and A-weighted sound pressure level data acquired by the multi-sensor (solid), the commercial device (dashed), and the reference instruments (dashed-dotted lines) during a one-day measurement campaign. were either too low, such as \(NO_{2}\), or lacked comparison data, such as formaldehyde, and thus, were not included in Figure 14.  
Concerning carbon dioxide, the measurements obtained by the developed multi-sensor are in good agreement with those from the reference instrument, with some peaks observed. Conversely, the commercial device tends to overestimate the actual concentration. As for TVOCs and PM 2.5/10, the measurements from the developed multi-sensor do not seem to capture certain transient events observed by the commercial device. Some differences among the measurements can be due to the experimental setup, as the devices were located in different position in the room, meaning that they experienced different IEQ parameters. More precisely, the increase of illuminance values detected by the multi-sensor, reported in solid line at the lower left of Figure 13, precedes those recorded by both the commercial device and the reference instrument. Such an early detection is attributed to the direct sunlight reaching the location of the multi-sensor before reaching those of the other devices.