###### Abstract
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Pollutant Class** & **Residential Buildings** & **Non-Industrial Buildings** \\ \hline \hline \multicolumn{3}{c}{**Bacterial**} \\ \hline Very low & \textless{}100 CFU/m\({}^{3}\) & \textless{}50 CFU/m\({}^{3}\) \\ Low & \textless{}500 CFU/m\({}^{3}\) & \textless{}100 CFU/m\({}^{3}\) \\ Mean & \textless{}2500 CFU/m\({}^{3}\) & \textless{}500 CFU/m\({}^{3}\) \\ High & \textless{}10,000 CFU/m\({}^{3}\) & \textless{}2000 CFU/m\({}^{3}\) \\ Very high & \textgreater{}10,000 CFU/m\({}^{3}\) & \textgreater{}2000 CFU/m\({}^{3}\) \\ \hline \hline \multicolumn{3}{c}{**Mycetic**} \\ \hline Very low & \textless{}50 CFU/m\({}^{3}\) & \textless{}25 CFU/m\({}^{3}\) \\ Low & \textless{}200 CFU/m\({}^{3}\) & \textless{}100 CFU/m\({}^{3}\) \\ Mean & \textless{}1000 CFU/m\({}^{3}\) & \textless{}500 CFU/m\({}^{3}\) \\ High & \textless{}10,000 CFU/m\({}^{3}\) & \textless{}2000 CFU/m\({}^{3}\) \\ Very high & \textgreater{}10,000 CFU/m\({}^{3}\) & \textgreater{}2000 CFU/m\({}^{3}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Microbiological pollution and IAQ assessment. \begin{table}
\begin{tabular}{c c} \hline \hline
**Concentration** & **Assessment** \\ \hline \textless{}0.200 mg/m\({}^{3}\) & Comfort level \\ \textless{}0.200–3 mg/m\({}^{3}\) & Acceptable level \\ \textless{}3–25 mg/m\({}^{3}\) & Discomfort level \\ \textgreater{}25 mg/m\({}^{3}\) & Unacceptable toxicity \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Concentration level of VOCs and their assessment. Finally, considering conditions for the well-being of people, [20; 21] report the typical average values of indoor air temperature, relative humidity, and mean air velocity (Table 5). Currently, there is no specific reference in the Italian national legislation, and no global and integrated policy has been defined in the technical field, for the evaluation of cause-effect associations between the presence, type, and concentration of pollutants and perceived discomfort/health risk, according to the above-mentioned requirements. However, there are some reference technical rules and standards, guidelines, and national and international studies on IAQ [18; 22; 23] that provide precise indications, e.g., ANSI/ASHRAE standard 62.1-2019 [24], where IAQ is defined as \"air in which there are no known contaminants at harmful concentrations, as determined by cognizant authorities, and with which a substantial majority (80% or more) of the people exposed do not express dissatisfaction\". Since discomfort and health risk are largely related to pollutant concentrations and, therefore, indirectly to the ventilation effectiveness in the rooms, many technical and regulatory provisions deal with minimum values of air flow rates [25; 26]. In addition, it is possible to find guidelines dealing with the hygienic maintenance of air handling units (filtration and cleaning) and the ductwork, relating to their inspection and cleaning procedures, and reference values on the concentration of dust, bacteria, and fungi inside the ductwork, as well as reports (mostly published by the Italian National Institute of Health--ISS) which deal with control and regulation in the IAQ arena to protect human health [12; 27; 28; 29]. In Italy, in museums, the protection of artworks and individuals fall under a very broad regulatory and legislative framework overseen from the Ministry for Cultural Heritage and Activities [30] to the Ministry of Health [31]. Guidelines are also available that are issued by various national public technical bodies, such as the Higher Institute for Prevention and Occupational Safety (ISPESL), the Italian National Health Institute (ISS), and other international bodies, such as the World Health Organization (WHO), the Air Infiltration and Ventilation Center (AIVC), and, finally, ANSS (Agence Nationale de Securite Sanitaire de l'Alimentation, de l'Environnement et du Travail--the national agency for health, food, environmental and work safety).