“Use of Filters and Special Materials in Classrooms, Based on the Assessment of the Presence of CO2 As an Indicator of Covid Reduction and Control in Closed Spaces = Uso De Filtros Y Materiales Especiales En Aulas, Basado En La evaluación De Presencia De CO2 Como Indicador De reducción Y Control De Covid En Espacios Cerrados”. Building & Management 5, no. 3 (December 8, 2021): 51–62. Accessed April 17, 2025. https://polired.upm.es/index.php/building_management/article/view/4714.