A heat exchanger having a stack of multiple plates which are parallel to one another and to a longitudinal direction, and stacked spaced apart from one another so as to define, between one another, a first series of passages for the flow of at least a first fluid in an overall flow direction parallel to the longitudinal direction, each passage being delimited by closure bars disposed between the plates. A filtering device is arranged in at least one passage of the first series, the filtering device extending for the one part between two adjacent plates defining the passage and for the other part between two of the closure bars delimiting the passage, the filtering device having a metal sheet material chosen from among a metal fabric, a nonwoven of metal fibres, a sintered metal powder or sintered metal fibres, a metal foam, or a microperforated plate.