A fan filter device (50) for a respirator (1) includes an air inlet (54) for unfiltered air and an air outlet (56) for the discharge of filtered air. A fan unit (60), for aspirating air through the air inlet, includes a fan motor (62) and a fan sensor (64). The fan sensor is designed for detecting at least one operating parameter of the fan motor. The fan filter device further includes a filter unit (31) for receiving a filter (30) for filtering the aspirated air and an air flow sensor (58) for detecting at least one flow parameter of the filtered air flowing through the air outlet. A control unit (66) is configured to monitor the fan motor as a function of the at least one flow parameter and the at least one operating parameter. A respirator and method for operating such a fan filter device are also provided.