## 6 Results and Analysis  
The graph below shows the evolution of CO2 levels and temperature in the classroom studied 5 without a ventilation system. There are wide variations in CO2 levels over the course of the day, generally fluctuating between 750 and 1500 ppm, with a peak between 7 and 10 a.m., at above 1500 ppm. As a reminder, the ideal CO2 level in a room is recommended to be less than 1000 ppm. The levels on this day are not satisfactory and show the need for a ventilation system to evacuate CO2 air to the outside. The level of CO2 in the air can also be used to assess classroom activity. Indeed, we know that CO2 is released by the people in the room as they breathe. Therefore, the more people there are in a room and the greater their physical activity, the faster the CO2 levels in the air will rise, saturating the air with CO2. As can be seen from Figure 6, the CO2 levels reach alarming values of more than 3000 ppm, while the air temperature, due to high internal gains, goes up to even 26 C. We remind the reader that the measurements took place in the middle of March 2023. For the entire set of measurements from 11 March 2023 to 11 April 2023, the average temperature was 23 C, with a maximum of 26 C and a minimum of 13.3 C during the nighttime on the weekend). For the CO2, the data showed maximum values of even 7036 ppm (20 March 2023 at 9:23 a.m.) while the average (including nighttime) was 845 ppm. The data shown in the graph (see Figure 6), which illustrate the change in carbon dioxide (CO2) levels and temperature within a classroom lacking a ventilation system, provide compelling evidence to support the necessity of conducting thorough investigations regarding the implementation of ventilation in educational settings. The variations in observed carbon dioxide (CO2) levels, namely the peaks that reach, in most of the cases, 3000 parts per million (ppm), greatly exceed the recommended maximum threshold of 1000 ppm. This divergence not only signifies inadequate air quality but also emphasizes the potential health and cognitive consequences for individuals in educational settings. The presence of values over 3000 ppm, occasionally peaking at 7036 ppm, suggests an environment that has the potential to significantly impede cognitive functions and impair  
Figure 6: Typical day in the non-ventilated classroom. learning efficiency. This is particularly worrisome considering that these measures were obtained in a conventional educational environment during standard school hours. Elevated temperatures, particularly when combined with elevated amounts of carbon dioxide, have the potential to induce discomfort, impair concentration, and ultimately diminish academic performance. The presence of these conditions in March, a month often associated with lower temperatures, suggests that the severity of the situation may be significantly amplified during periods of higher temperatures. This highlights the pressing necessity for the implementation of efficient ventilation systems in educational environments, with the aim of guaranteeing the comfort, health, and cognitive well-being of all present. The research presented in this study makes a substantial contribution to the ongoing academic discussion surrounding indoor environmental quality in educational settings, as in this paper, we are focusing on possible solutions. The study of four distinct ventilation systems inside a classroom environment has yielded noteworthy findings about their efficacy in preserving indoor air quality and controlling the temperature (see Figure 7). Figure 7: Typical day in the ventilated classrooms. System 1 has shown remarkable efficacy by consistently upholding CO2 concentrations below 1000 ppm for 97% of the duration, thereby serving as a robust metric for assessing favorable indoor air quality. Nevertheless, it is important to highlight that the temperature within the room increased to 27 \({}^{\circ}\)C, which is marginally higher compared to that with the other systems.