Fan filter unit, respiratory protection system and method

The invention relates to a fan filter unit (50) for a respiratory protective system (1) and a corresponding respiratory protection system (1). The blow filter device (50) comprises an air inlet (54) for flow of unfiltered air and an air outlet (56) for outflow of filtered air. A blower unit (60) for sucking air through the air inlet (54) includes a fan motor (62) and a blower sensor (64), wherein the blower sensor (64) for detecting at least one operating parameter of the fan motor (62) is formed. The blow filter device (50) further comprises a filter unit (31) for receiving a filter (30) for filtering the sucked air and an air flow sensor (58) for detecting at least one flow parameter of through the air outlet (56) flowing filtered air. A control unit (66) is formed by at least at least to control the blower motor (62) in dependence of a flow parameter and the one operating parameter. The invention further relates to a method for operating a powered air purifying device (50).