Abstract: A diffuser-type air freshener apparatus or appliance (1, 100) affixed to an air grille (6) of a domestic or industrial central air handling system. The appliance includes a housing module which may include a reservoir (24) for storing a volatile fragrant liquid into which one or more scent-wicks (8, 108) are adjustably immersed. Alternatively, dry or pre-moistened wicks may be employed and selectively added or removed to obtain the desired level of scent diffusion. Alternatively, the appliance housing defines an inner opening (42) through which air passes when returning along a defined airflow direction (A) to the central system. One or more flat scent elements or wicks are disposed such that their major flat wicking sides (9) are oriented generally along the defined airflow direction, affording substantial diffusing and/or wicking action with minimal interference with system airflow.