A device (100; 200) for the sterilization of a gas, comprising: - a sterilization chamber (110,110'; 210) with an inlet and an outlet and a flow direction between said inlet and said outlet; - a ventilation system configured and adapted to let the gas flow from said inlet to said outlet; - one or more sources of at least one laser beam (115,115'; 215) positioned so that said at least one laser beam (115,115'; 215) passes through said sterilization chamber (110,110'; 210); and - said at least one laser beam (115, 115'; 215); wherein: - said at least one laser beam (115,115'; 215) has a wavelength alternatively in a range of ± 15% around 1940nm, 2950nm, 9300nm, 10600, and a predetermined irradiance; - the sterilization chamber (110,110'; 210) comprises a system of mirrors (112,113; 212,213) configured and adapted to create a network of laser segments inside the sterilization chamber; - said laser segments are incident with respect to said flow direction; and - said ventilation system is configured and adapted to let the gas flow with a speed which depends on the number of said laser segments, as well as on the wavelength and on said predetermined irradiance of said at least one laser beam; the device being characterized in that: - said at least one laser beam (115,115'; 215) is introduced in said sterilization chamber (110,110'; 210) with a first inclination (a) from 0.2 to 1° or from 1 to 15° with respect to a direction perpendicular to said flow direction; - said at least one laser beam (115, 115'; 215) is introduced at a first end of the sterilization chamber (110,110'; 210) along said flow direction and is reflected by at least one respective mirror (114, 114') inclined at a second end of the sterilization chamber (110, 110'; 210) along said flow direction, opposite to said first end, with a second inclination (β) from 0.2 to 1° or from 1 to 15° with respect to said perpendicular direction, wherein said second inclination (β) differs from said first inclination (α). - a sterilization chamber (110,110'; 210) with an inlet and an outlet and a flow direction between said inlet and said outlet; - a ventilation system configured and adapted to let the gas flow from said inlet to said outlet; - one or more sources of at least one laser beam (115,115'; 215) positioned so that said at least one laser beam (115,115'; 215) passes through said sterilization chamber (110,110'; 210); and - said at least one laser beam (115, 115'; 215); - said at least one laser beam (115,115'; 215) has a wavelength alternatively in a range of ± 15% around 1940nm, 2950nm, 9300nm, 10600, and a predetermined irradiance; - the sterilization chamber (110,110'; 210) comprises a system of mirrors (112,113; 212,213) configured and adapted to create a network of laser segments inside the sterilization chamber; - said laser segments are incident with respect to said flow direction; and - said ventilation system is configured and adapted to let the gas flow with a speed which depends on the number of said laser segments, as well as on the wavelength and on said predetermined irradiance of said at least one laser beam; - said at least one laser beam (115,115'; 215) is introduced in said sterilization chamber (110,110'; 210) with a first inclination (a) from 0.2 to 1° or from 1 to 15° with respect to a direction perpendicular to said flow direction; - said at least one laser beam (115, 115'; 215) is introduced at a first end of the sterilization chamber (110,110'; 210) along said flow direction and is reflected by at least one respective mirror (114, 114') inclined at a second end of the sterilization chamber (110, 110'; 210) along said flow direction, opposite to said first end, with a second inclination (β) from 0.2 to 1° or from 1 to 15° with respect to said perpendicular direction, wherein said second inclination (β) differs from said first inclination (α).