This paper describes the implementation of a series of ventilation strategies in a nursery and primary school from September 2020, when the government decided to resume the students’ face-to-face activity in the middle of a COVID scenario. Air quality and hygrothermal comfort conditions were analysed before the pandemic and compared for different ventilation configurations in a post-COVID scenario. Ventilation strategies included the protocols issued by the Public Administration, while others were developed based on the typological configuration and use of the school. Results revealed that it is advisable to implement certain strategies that reduce the risk of infection among the occupants of the spaces, without a significant decrease in hygrothermal comfort. Given the importance of maintaining better IAQ in the future within classrooms, and regarding the pre-COVID situation, these strategies may be extended beyond this pandemic period, through a simple protocol and necessary didactic package to be assumed by both teachers and students of the centre.

The most recent research confirms that airborne transmission may be the dominant mode of SARS-CoV-2 virus spread in the interior spaces of buildings. Consequently, based on some prescriptions that implemented natural ventilation during face-to-face lessons in a university centre, an experimental characterization of several complementary options aimed at reinforcing the prevention and safety of the occupants was carried out. The action protocol adopted was based on the combination of mandatory natural ventilation, a maximum contribution of outdoor air supply in the air conditioning system, and the use of filtering devices located inside the classroom. All the strategies were incorporated concomitantly with necessary compliance with the basic conditions of social distance, occupation, use of masks and guidelines for use and cleaning within educational buildings. The suitability of this protocol was further evaluated throughout the teaching day with students and teachers by measuring the CO₂ concentration. The results showed that the measures implemented successfully removed the possible pollutants generated inside.