## 2 Materials and Methods
### The Determination of the Microclimate Characteristics  
The internal microclimate was determined in both rooms of the church, as well as in its immediate vicinity, in order to correlate the values obtained inside with those outside. Thus, the analyzed indicators were temperature T, RH, the concentration of CO\({}_{2}\), particulate matter (PM\({}_{2.5}\), PM\({}_{10}\)), the total amount of volatile organic compounds (VOCs), formaldehyde (HCHO), and natural light (NL). These indicators were analyzed due to the fact that they represent factors with a high destructive potential on natural stone if they are not kept within normal limits.  
The data were collected over a period of 12 weeks between April and June 2024. The monitoring was carried out in this period in order to capture the conditions characteristic of spring and early summer, when T and RH fluctuations are significant and favor microbial activity, thus contributing to stone deterioration. This period offers the opportunity to observe the direct impact of variable microclimatic conditions on biodeterioration.  
Two different techniques were individualized to determine the indicators. For the determination of PM\({}_{2.5}\), PM\({}_{10}\), VOC, HCHO, and NL, the data were collected manually using 13 individual points (12 inside the church and 1 outside). The values were determined at three different times of the day: in the morning (7), at midday (13), and in the evening (19). The data collection points were positioned in such a way as to obtain the best possible coverage of the rooms, leaving at the same time the possibility of performing some analyses of the distribution of these parameters at the level of the church (Figure 3a). T, RH, and CO\({}_{2}\) were monitored using two data logger sensors, which aimed to record data automatically. All sensors were set to capture data at hourly intervals to obtain as large of a database as possible. One sensor was positioned inside the first room of the church, and the second was positioned at the entrance to the monument (Figure 3a).  
T, RH, and CO\({}_{2}\) were determined using two Extech SD800 type datalogger devices (Extech Instruments, Nashua, NH, USA). The accuracy of the device is \(\pm\)40 ppm for CO\({}_{2}\) concentration measurement, \(\pm\)0.8 \({}^{\circ}\)C for T measurement, and \(\pm\)4% for RH determination. The data collection was performed at a 1 m distance from the ground, the sampling time being 1 min/point, and the average of all values obtained for that minute being validated.  
Total air volume PM concentration was determined using a PCE-PCO 2 portable device (PCE Instruments UK, Southampton, UK). This instrument has the capability to analyze indoor air samples and display the concentration of suspended particles separately for the sizes of 0.3 \(\upmu\)m, 0.5 \(\upmu\)m, 1.0 \(\upmu\)m, 2.5 \(\upmu\)m, 5.0 \(\upmu\)m, and 10 \(\upmu\)m. In the present study, only particles with sizes of 2.5 \(\upmu\)m and 10 \(\upmu\)m were analyzed. The device determines the indicators with an error of up to 5% and allows the saving of 5000 data sets in the internal memory. The air sampling time to determine the concentration of PM\({}_{2.5}\) and PM\({}_{10}\) was 30 sec/collection point.  
VOC and HCHO concentrations were determined using a BLATN BR-smart-123s device (BLATN Science and Technology, Beijing, China). It has measuring ranges between 0 and 5.0 mg/m\({}^{3}\) for HCHO and between 0 and 9.9 mg/m\({}^{3}\) for VOCs. The measurement resolution for both indicators was 0.001 mg/m\({}^{3}\), and the margin of error was up to \(\pm\)5%.  
NL was measured three times a day using an Extech SDL400 datalogger lux meter (Extech Instruments, Nashua, NH, USA). This device indicates the amount of light in lux, with an accuracy of \(\pm\)4%, having the ability to save the recorded values.  
ArcGIS 10.8.2, Matlab R2024a, and Microsoft Excel 6.2.14 programs were used to analyze the obtained values.