###### Abstract  
The assessment of indoor air quality (IAQ) in museums is a complex issue. In this study, a comprehensive investigation methodology was defined and applied to a museum to be validated. This methodology includes the analysis of exposed objects, the optimal conditions for conservation, the building features and the HVAC systems, and the indoor thermo-hygrometric and air quality conditions. In 2019, a survey in the Uffizi Gallery of Florence, one of the most important museums in the world, was carried out to assess the IAQ conditions in the museum, and the workers and visitors' well-being, by focusing on some representative rooms (nine) of the museum complex in terms of visitor turnout and HVAC systems, including rooms closed to the public. Since IAQ is related to the possible presence and concentration of chemical and biological pollutants, these indicators, as well as thermo-hygrometric parameters, were monitored. The monitoring results were analyzed, evaluated, and compared with those suggested by the literature, guidelines and legislative documents dealing with IAQ in museums. Monitoring approaches for deepening investigations, as well as guidelines aimed at improving IAQ in the Uffizi Gallery and similar buildings are proposed. indoor air quality; monitoring; museum; cultural heritage; artworks conservation; user well-being +
Footnote †: journal: Medical  
Carbon dioxide (CO\({}_{2}\)) and water vapour are emitted from human breath and can be used as an indicator of pollution caused by human beings and of the effectiveness of ventilation in a museum [11]. It has very little adverse effect on collections, though concentrations above 1000 ppm can have adverse effects on human health. Table 1 shows concentration levels of CO\({}_{2}\) and their assessment [12]. Most of the pollutants surveyed in museums belong to the class of VOCs, such as aliphatic, aromatic, and chlorinated hydrocarbons, aldehydes, terpenes, alcohols, esters, and ketones. They can be found in indoor air in relation to the activities performed, to the structural characteristics, to the HVAC system features, and to crowding. In general, the principal sources of VOCs are the occupants, HVAC equipment, air intakes near traffic-polluted areas, cleaning products, draperies, environmental tobacco smoke (ETS), printers and copiers, building materials, and furnishings [12; 13]. In Table 2, the most common indoor VOCs are listed with their main sources. High concentrations of VOCs in indoor environments, that can be two to five times higher indoors than outdoors [14], can cause a wide range of health effects. The most common effects on human health can be caused by short-term as well as long-term exposure to pollutants. An interesting review of the issues related to exposure to cleaning products and air fresheners is provided in [15], where different groupings of substances are identified, including glycols, aliphatic, and aromatic hydrocarbons, aldehydes, ketones, and chlorinated organics. Detergents and sanitizers are often considered non-hazardous, pursuant to regulation 1272/2008 (CLP) [16]. For this reason, the labels and safety data sheets do not report the chemical name of the individual substances, but their general composition (detergent, perfume, etc.). This does not allow for specific determination of the possible contribution of solvents deriving from these uses. With respect to exposure to indoor air VOCs, the European Guideline COST Project 6 1 3--Report No. 11 [17] reports the values of total volatile organic compounds (VOCs) derived from international studies (Table 3). For microbiological pollutants, the bioaerosol mainly consists of vital and non-vital biological agents, their metabolites (enzymes and toxins), bacterial and fungal spores and \begin{table}
\begin{tabular}{c c} \hline
**Concentration** & **Assessment** \\ \hline \(<\)1000 ppm & Acceptable levels \\
1000–2000 ppm & High levels \\ \(>\)2000 ppm & Unacceptable levels \\ \hline \end{tabular}
\end{table}