An experiment was performed to determine whether the sensory pollution emitted from a bagfilter that had been used for 3 months in a suburban area in Denmark was influenced bydifferent ways of operating the air-handling unit (AHU). Samples of the used filter were preconditioned to simulate three operating conditions: (1) switched off overnight; (2) airflowreduced to 10% overnight; and (3) continuous 100% operation. Outside air passed through thesamples and the acceptability of the air after the filter was assessed by a panel of subjects. Theresults indicate that turning off the AHU or reducing the airflow outside working hours wouldsignificantly increase the sensory pollution emitted by a used bag filter immediately after theAHU is turned on, in comparison with continuous airflow through the AHU (P < 0.05). Afteroutside air had been passed through the filter for 2 h, no significant differences were found.