An electric switching unit comprises a casing and a plurality of arc extinguishing chambers formed inside the casing, each arc extinguishing chamber comprising a gas discharge orifice opening to outside the casing. The electric switching unit comprises a filtering device positioned outside the casing and comprising: a plurality of inlet openings placed on a lower region of the filtering device, each one being configured to collaborate fluidically with one of the said gas discharge orifices; an outlet opening placed on a lateral region of the filtering device; a common internal chamber which places the inlet openings in fluidic communication with the outlet opening; and a filter located inside the internal chamber between the inlet openings and the outlet opening.