The resistance to airflow of air filters for removing particulate matter causes energy implications and consequently the operating cost of heating, ventilating and air-conditioning (HVAC) systems. The objective of this dissertation is to determine the energy implications of air cleaning devices installed in the air handling unit (AHU) of a large classroom at Politecnico di Torino, with particular attention to the several sets of fine-filters used from 2010 to 2018. It was concluded that with the aging of the fine-filter is generated a decrease in the fan electric power draw (since the system is at constant volume, CAV), bringing with it possible energy savings.