A laundry drying appliance comprising: - a cabinet; - a laundry chamber rotatably enclosed within the cabinet for containing laundry to be dried; - a drying air flow system for passing said air through the laundry chamber, said drying air flow system comprising an air demoisturizing unit configured to demoisturize said air; - a filter seat arranged within the drying flow system for removably receiving an air filter; - said air filter being movable from a first position wherein it is inserted into said filter seat to filter drying air leaving the laundry chamber, to a second position wherein it is removed from said filter seat and detached from the appliance and viceversa; - said laundry drying appliance being configured to operate in a laundry dryer mode when the air filter is in the first position, and in an ambient air dehumidification mode to dehumidify air in the ambient outside the cabinet when the air filter is said second position; characterised in that: the laundry drying appliance further comprises a movable wall system arranged within said filter seat and operable, by moving said air filter from one to the other of said first and second positions, to configure the drying air flow system such that: - when the air filter is said first position, the drying air flow system is configured to circulate drying air in a substantially closed air circuit, through the laundry chamber and the air filter, and - when the filter is said second position, the laundry chamber is put in fluid communication with the ambient outside the cabinet by means of an air introduction opening ( IN) and an air exhausting opening ( OUT) provided by the movable wall system in the filter seat, wherein said movable wall system is configured so that, when the air filter is in said second position, the operation of the movable wall system causes the volume of the filter seat to be split in: - a first volume portion comprising said air introduction opening ( IN) and guiding air from the ambient outside the cabinet to the laundry chamber, and - a second volume portion comprising said air exhausting opening ( OUT) and guiding air from the laundry chamber to the ambient outside the cabinet substantially without mixing with air flowing in the first volume portion. - a cabinet; - a laundry chamber rotatably enclosed within the cabinet for containing laundry to be dried; - a drying air flow system for passing said air through the laundry chamber, said drying air flow system comprising an air demoisturizing unit configured to demoisturize said air; - a filter seat arranged within the drying flow system for removably receiving an air filter; - said air filter being movable from a first position wherein it is inserted into said filter seat to filter drying air leaving the laundry chamber, to a second position wherein it is removed from said filter seat and detached from the appliance and viceversa; - said laundry drying appliance being configured to operate in a laundry dryer mode when the air filter is in the first position, and in an ambient air dehumidification mode to dehumidify air in the ambient outside the cabinet when the air filter is said second position; the laundry drying appliance further comprises a movable wall system arranged within said filter seat and operable, by moving said air filter from one to the other of said first and second positions, to configure the drying air flow system such that: - when the air filter is said first position, the drying air flow system is configured to circulate drying air in a substantially closed air circuit, through the laundry chamber and the air filter, and - when the filter is said second position, the laundry chamber is put in fluid communication with the ambient outside the cabinet by means of an air introduction opening ( IN) and an air exhausting opening ( OUT) provided by the movable wall system in the filter seat, - when the air filter is said first position, the drying air flow system is configured to circulate drying air in a substantially closed air circuit, through the laundry chamber and the air filter, and - when the filter is said second position, the laundry chamber is put in fluid communication with the ambient outside the cabinet by means of an air introduction opening ( IN) and an air exhausting opening ( OUT) provided by the movable wall system in the filter seat, wherein said movable wall system is configured so that, when the air filter is in said second position, the operation of the movable wall system causes the volume of the filter seat to be split in: - a first volume portion comprising said air introduction opening ( IN) and guiding air from the ambient outside the cabinet to the laundry chamber, and - a second volume portion comprising said air exhausting opening ( OUT) and guiding air from the laundry chamber to the ambient outside the cabinet substantially without mixing with air flowing in the first volume portion. - a first volume portion comprising said air introduction opening ( IN) and guiding air from the ambient outside the cabinet to the laundry chamber, and - a second volume portion comprising said air exhausting opening ( OUT) and guiding air from the laundry chamber to the ambient outside the cabinet substantially without mixing with air flowing in the first volume portion.