A sensor includes an inner channel with: a first portion; a second portion in communication with the first portion; a storage zone in communication with the first portion; a baffle plate extending inside the first portion; the first portion and the baffle plate being sized such that, in an air stream entering the sensor through a first, open end of the first portion and containing first particles with a diameter of 10 μm or less and second particles with a diameter of more than 10 μm, the first particles reach the second portion of the inner channel while the second particles reach the storage zone.