BTEX near real-time monitoring in two primary schools in La Rochelle, France.

The present field campaign was conducted in two French primary schools for 5 weeks, where the experimental conditions were modified every week. During the first week, the classrooms were empty and not occupied, whereas the furniture was added the second week. For the three last weeks, the classrooms were normally occupied by students and various scenarios of ventilation were applied. BTEX concentrations were monitored by using novel portable pre-industrial prototypes with low gas and energy consumption, which worked continuously and operated in near real time with a time resolution of 10 min. The BTEX concentrations were compared to CO₂ measurements since the latter is commonly considered as a confinement indicator. In both schools, BTEX were not detected during the absence of students indicating that neither building materials nor furniture emit such compounds. Once the schools occupied by students, BTEX have been detected from time to time, and their concentrations ranged as follows: 0-12 ppb (benzene); 0-29 ppb (toluene), 0-4 ppb (ethylbenzene), 0-11 ppb (m/p-xylenes), and 0-10 ppb (o-xylene) excluding huge values due to paint emissions in one of the schools. Toluene was found to be strongly correlated to high levels of CO₂, showing that it was emitted by internal students activities scheduled at the end of mornings. On the contrary, benzene peak was not correlated to high values of CO₂, suggesting that it comes from external sources. [ABSTRACT FROM AUTHOR]