## 8 Conclusions and Future Work  
The comparative analysis of carbon dioxide (CO\({}_{2}\)) levels in classrooms equipped with various ventilation systems, as opposed to a scenario without any ventilation, over a period of one month, offers a distinct signal regarding the efficacy of these systems in upholding satisfactory indoor air quality throughout school hours. Our study led to a few significant results regarding the assessment of decentralized ventilation systems in educational environments. First and foremost, these systems exhibit a high level of efficacy in improving air quality, successfully controlling CO\({}_{2}\) levels to ensure that they remain below acceptable thresholds. This is of crucial significance for the physical and cognitive wellbeing of both students and staff members. One significant constraint that has been identified is the absence of adequate humidity regulation. In specific instances, this phenomenon has led to a decrease in indoor humidity levels that fall below the optimal range, which may have potential implications for both comfort and health. In relation to noise levels, it can be observed that the systems do not consistently maintain compliance to the 35 dB(A) noise threshold when operating at their maximum air supply capacity. However, these systems are able to sustain satisfactory acoustic conditions when run within a moderate range of levels, specifically at 55% or between 320 to 380 m\({}^{3}\)/h. The absence of any complaints from occupants regarding noise or air drafts is a notable characteristic, suggesting a general satisfaction with the ambient conditions facilitated by these technologies. The systems' ease of installation and non-invasive characteristics makes them a highly favorable choice when retrofitting existing school structures. The incorporation of this characteristic, alongside with its cost-efficiency, taking into account the significant advantages for the well-being of children and decreased energy usage, puts up a compelling rationale for its implementation. The expenses associated with implementing these systems in classrooms, varying from 4000 to 6500 Euros, can be considered very affordable when considering the positive impact on health and the environment. This is particularly significant as these systems effectively eliminate the necessity for window ventilation. An effective ventilation strategy that has emerged from our study is the use of boost mode during break times or periods of high background noise. This methodology aims to enhance air quality while minimizing any possible adverse effects on classroom activity. Nevertheless, it is apparent that humidifiers are essential throughout the winter season in order to uphold indoor humidity levels at above 40%, thereby effectively resolving the problem of low humidity induced by these systems. Similar measurement campaigns in schools could be found in the literature, concerning the evolution of indoor CO\({}_{2}\) concentrations, temperature, and relative humidity. For instance, [PERSON] et al. [38] performed an extensive experimental study in four schools from Serbia (three located in urban areas and one in a rural area), with the results showing a good correlation in terms of CO\({}_{2}\) concentration profiles with the results outlined in this paper (Figure 6). The authors showed a strong correlation between the indoor temperature, humidity, and CO\({}_{2}\) concentration for naturally ventilated classrooms, while for the mechanical ventilation case, all these parameters are under control, and this correlation is much weaker. [PERSON] [39] arrived at a similar conclusion in a study of IAQ and thermal comfort performed for a kindergarten case. Similar results were found by [PERSON] et al. [8] in a study of the evaluation of different natural ventilation strategies using CO\({}_{2}\) sensors to monitor IAQ in classrooms and by [PERSON] et al.