## 3 Results and Discussion
### Indoor Air Quality  
Indoor air quality levels were also investigated in the halls of the museum. CO\({}_{2}\) and TVOC concentrations were measured and compared to the ASHRAE Standard 62.1-2010 [38] (American Society of Heating, Refrigerating and Air-Conditioning Engineers) proposed CO\({}_{2}\) limit of 1000 ppm and TVOC tolerance limits as reported by [PERSON] et al. [39]. As \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Experimental Point** & \multicolumn{3}{c}{**Cold Period (October-April)**} & \multicolumn{3}{c}{**Warm Period (May–September)**} \\ \hline  & 2019 & 2020 & 2021 & 2019 & 2020 \\ Auditorium & 15\% & 5\% & 7\% & 28\% & 19\% \\ Entrance & 6\% & 4\% & 5\% & 41\% & 15\% \\ Law & 18\% & 5\% & 6\% & 45\% & 26\% \\ Medicine & 15\% & 2\% & 2\% & 37\% & 21\% \\ Pr. Room & 3\% & 0\% & 0\% & 17\% & 28\% \\ Dentistry & 1\% & 1\% & 0\% & 45\% & 25\% \\ Offices & 51\% & 40\% & 33\% & 18\% & 25\% \\ Philosophy & 20\% & 15\% & 4\% & 37\% & 15\% \\ App. Science & 20\% & 20\% & 7\% & 27\% & 16\% \\ Museum (in total) & 17\% & 10\% & 7\% & 33\% & 21\% \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Percentages of indoor temperature measurements within the recommended limit ranges for the entire experimental period. depicted in Figure 6, the CO\({}_{2}\) levels were found to be within the respective limits, with the Offices (473 ppm) and the Auditorium Hall (472 ppm) on the ground floor depicting the highest average CO\({}_{2}\) concentration. This observation can be attributed to the fact that the offices were constantly full of the museum's personnel, especially before COVID-19 restriction measures were implemented. What is more, prior the pandemic and during the time between the 1 st and the 2 nd lockdown, events were often hosted in the Auditorium, and renovations continued to be conducted during the pandemic. Nevertheless, even the outliers that were mostly associated with such events are well below the ASHRAE limits, indicating the lack of a mechanical ventilation system, which would improve the indoor conditions. In the same Figure, one may notice that the outdoor mean concentration of CO\({}_{2}\) reached 443 ppm, which is very close to the values of the indoor environment. Thus, natural ventilation (openings) seems to play a key role in the building's microclimatic conditions. Combined with the results of T and RH, a renovation strategy that includes the installation of a state-of--the-art mechanical ventilation system is proposed, not only to retain low levels of CO\({}_{2}\) but also to maintain adequate thermal conditions for the occupants by avoiding the frequent opening of doors and windows. The calculation of the air exchange rates with the use of blower door and/or tracer gas methods in each room may be considered as a next step for future monitoring campaigns within this building in order to obtain more detailed results on ventilation rates during different periods. The average CO\({}_{2}\) concentrations in the exhibition halls of both floors were found at 445 ppm and 450 ppm, respectively. Both the Entrance of the museum (450 ppm) and the Applied Sciences hall (450 ppm) recorded the highest concentrations amongst the halls of their respective floors and remained well below the abovementioned limit (Figure 7). Figure 6: Carbon dioxide concentrations in the museum halls and outdoors. “**” symbol is used for the outliers. The first floor recorded the highest concentration of TVOC, with 5 ppm, which can be attributed to the combination of using cleaning products along with the insufficient ventilation of the Presentation Room (11 ppm) and Dentistry Hall (9 ppm). One also may notice that the area with the second highest concentration of TVOC was the Auditorium (5 ppm), which also had the 2 nd highest concentration of CO\({}_{2}\); however, these levels were still well below the threshold limits (Figure 8). However, this was not the case for the 1 st and 2 nd floors, where there were some cases where the TVOC limits were surpassed.