# Air Quality Assessment of a School in an Industrialized Area of Southern Italy
## 3 Results and Discussion
### VOC Distribution in the Different School Areas Investigated and Their Temporal Variability
It is worth noting that toluene shows the same trend both outdoors and indoors, indicating an outdoor origin. Benzene, as well as alkylbenzenes, xylenes, and ethylbenzene are characterized by different indoor trends (Figure 5) if compared to the outdoor values (Figure 4), apart from the first two periods. For site B2, different indoor trends (Figure 6) were observed with respect to classroom 4E. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**VOC** & **Caverage Indoor (\(\mu\)g m\({}^{-3}\))** & **Caverage Outdoor (\(\mu\)g m\({}^{-3}\))** & **I/O** \\ \hline Benzene & 1.94 & 3.23 & 0.60 \\ Toluene & 0.81 & 0.53 & 1.52 \\ Ethlybenzene & 0.08 & 0.03 & 2.67 \\ Alkylbenzenes & 0.29 & 0.28 & 1.04 \\ Xylene & 0.18 & 0.05 & 3.60 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Benzene, Toluene, Ethylbenzene, Alkylbenzenes, and Xylene indoor and outdoor mean concentration values. Figure 3: Benzene, Toluene, Ethylbenzene, Xylene, and Alkylbenzenes indoor mean concentration values over the entire monitoring period in the different school areas investigated. B1 indicates the male bathroom site, B2 the female bathroom site, 4B the classroom 4B, 4E classroom 4E, and O4E the external balcony outside classroom 4E. Figure 4: Mean VOC concentration for each sampling period on site O4E (balcony of classroom 4E). Figure 5: Mean VOC concentration values for each sampling period on site 4E (classroom 4E). Figure 6: Mean VOC concentration values for each sampling period on site B2. Toluene/Benzene ratios (T/B) (reported in Figure 7) have been used to distinguish different sources. Many studies agree that the main outdoor sources of BTEX are industrial activities and vehicular traffic [18,19]. In particular, a ratio below 2 indicates that the pollutants mainly derive from vehicular emissions or biomass combustion, while ratios above 2 indicate the presence of contributions from sources such as industrial emissions [18]. [PERSON] et.al. [20] state that if the B/T ratio is greater than 1 (i.e., T/B lower than 1), biomass combustion is likely to be the main source. This is also confirmed by [PERSON] et.al. [21], who found higher benzene concentrations than toluene ones when wood burning was the main source. In general, typical T/B ratio values reported in literature studies fall in a range between 0.8 and 6 [18,19,22]. As can be seen, the T/B ratios found at locations B1, B2, and 4B are higher with respect to 4E and the outdoor site. For site 4B, for which the ratio is higher than 1, a possible contribution from outdoor traffic is plausible. For sites B1, B2, 4E, and O4E, even if these values could be compatible, according to the literature [20], with sources such as biomass burning, some other contribution due to specific indoor sources could be present. In fact, it is very likely that the high concentrations of benzene at both locations 4E and O4E are related to emissions from cigarette smoke. This is because the balcony of classroom 4E overlooks the main atrium of the school where students gather during break periods, and cigarette smoke is, therefore, responsible for the high concentrations of benzene found. In fact, it has been shown that air concentrations of benzene from this source exceeds those of toluene, and that benzene is the VOC emitted in the highest quantities by cigarette smoke [23].