# Air Quality Assessment of a School in an Industrialized Area of Southern Italy
## 2 Materials and Methods
### Sampling Equipment and Data Collection Procedure
#### 2.2.2 Volatile Organic Compounds: Real-Time Monitoring  
High temporal resolution monitoring of TVOC concentrations (ppm), temperature (\({}^{\circ}\)C), and relative humidity (\(\%\)) was performed inside the selected educational buildings through the deployment of Photo Ionization Detectors (PIDs) ([PERSON], IonScience Ltd., UK). The PIDs' high-sensitivity technology comprises a Kripton UV lamp operating at 10.6 eV ionization potential, two collecting electrodes, and an electric-signals converter to measure TVOC concentrations within the 0.01 to 50 ppm concentration range with an accuracy of \(134\pm 5\) ppb, and a limit of detection (LOD) equal to 5 ppb. The PIDs featured built-in humidity compensation, thanks to the integration of humidity and temperature sensors and, thus, they automatically provided TVOC concentrations corrected for relative humidity. Before deployment inside the investigated schools, and to ensure data quality, the PIDs were factory calibrated using isobutylene as the calibration gas (thus, TVOC concentrations are herein expressed and discussed in ppmv isobutylene equivalent). During the monitoring campaign, TVOC concentrations were recorded with a 1 sec time resolution and were successively averaged on a 15 min time-frame for data analysis. The selection of the monitoring locations inside the selected classrooms was carefully decided according to representativeness criteria. Moreover, with specific regard to classroom 4E, indoor-outdoor simultaneous monitoring of TVOC concentrations was carried out by placing one PID inside the classroom and another on the external balcony. Inside the classroom, the detector was placed near the occupants' breathing zone, approximately 1 m above the floor and at least 2 m away from windows, doors, or active heating systems. The selection of the monitoring location was carefully decided to make the readings as representative of the whole room volume as possible. A distance of at least 2 m between the windows and the detector was guaranteed to avoid any air turbulence near the monitoring system, which could result in potential fluctuations in data readings. Outdoor measurements were taken to set the reference outdoor concentrations. 2.3 Determination of Radiello Volatile Organic Compounds by Gas Chromatography--Mass Spectrometer (GC-MS)  
Volatile organic compounds were extracted from the cartridges using 2 mL of carbon disulfide (CS\({}_{2}\)) and by stirring the solution from time to time over 30 min, both manually and with the aid of a mechanical stirrer (Vortex, VWR Collections). The extraction solvent was prepared to contain the internal standards (1,2-dichloroethane-d4, toluene-d8, 4-bromofluorobenzene) at a concentration of 5 g mL\({}^{-1}\). \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Sampling Period** & \multicolumn{6}{c}{**VOC Sampling**} & \multicolumn{6}{c}{**TVOC Sampling**} \\ \hline  & **Site** & **Site** & **Site** & **Site** & **Site** & **Site** & **Site** \\ \hline
1–5 February 2019 & B1 & B2 & 4B & 4E & O4E & 4E & O4E \\
5–8 February 2019 & B1 & B2 & 4B & 4E & O4E & 4E & O4E \\
8–12 February 2019 & B1 & B2 & - & 4E & O4E & 4E & O4E \\
12–15 February 2019 & B1 & B2 & - & 4E & O4E & 4E & O4E \\
15–19 February 2019 & B1 & B2 & - & 4E & O4E & 4E & O4E \\
19–22 February 2019 & - & B2 & - & 4E & O4E & 4E & O4E \\
22–26 February 2019 & - & B2 & - & 4E & O4E & 4E & O4E \\
26 February–1 March 2019 & - & B2 & - & 4E & O4E & - & - \\
1–5 March 2019 & - & B2 & - & 4E & O4E & - & - \\
5–12 March 2019 & - & B2 & - & 4E & O4E & - & - \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Sampling time schedule in the different school places: B1 (male bathroom), B2 (female bathroom), 4B (classroom 4B), 4E (classroom 4E), and O4E (external balcony classroom 4E). The analysis was performed using the gas chromatography-mass spectrometry technique (Agilent Technologies Inc. 8890 GC System, Santa Clara, CA, USA) with a DB-624 column (60 m \(\times\) 0.25 mm i.d. and 1.4 m film thickness), using helium as carrier gas.