A blade system for fans for industrial use, comprising: - a blade, which extends longitudinally along a first reference axis and defines within it a cavity, wherein said blade has a cross section with flattened profile and is oriented with a major dimension along a second reference axis; and - a supporting unit, on which said blade is fixed and which is inserted within the cavity of said blade, said supporting unit being designed to be connected to the rotor of a fan, wherein said cavity of said blade has a cylindrical conformation and a cross section with flattened profile and is oriented with a major dimension along said second reference axis; said blade system being characterized in that: said supporting unit comprises a tubular bar, which has a cross section with flattened profile and is oriented with a major dimension along said second reference axis, wherein the cross section of said tubular bar has a profile comprising two circular portions (16A, 16C) joined together by two opposed intermediate portions (16B, 16B'), and wherein said two circular portions (16A, 16C) each reproduce an arc of a circle defined by an angle greater than 180°, even more preferably greater than 270°, or else said supporting unit comprises a first tubular bar and a second tubular bar with circular cross section, which are arranged alongside one another along said second reference axis. - a blade, which extends longitudinally along a first reference axis and defines within it a cavity, wherein said blade has a cross section with flattened profile and is oriented with a major dimension along a second reference axis; and - a supporting unit, on which said blade is fixed and which is inserted within the cavity of said blade, said supporting unit being designed to be connected to the rotor of a fan, wherein said cavity of said blade has a cylindrical conformation and a cross section with flattened profile and is oriented with a major dimension along said second reference axis; said blade system being characterized in that: said supporting unit comprises a tubular bar, which has a cross section with flattened profile and is oriented with a major dimension along said second reference axis, wherein the cross section of said tubular bar has a profile comprising two circular portions (16A, 16C) joined together by two opposed intermediate portions (16B, 16B'), and wherein said two circular portions (16A, 16C) each reproduce an arc of a circle defined by an angle greater than 180°, even more preferably greater than 270°, or else said supporting unit comprises a first tubular bar and a second tubular bar with circular cross section, which are arranged alongside one another along said second reference axis. said supporting unit comprises a tubular bar, which has a cross section with flattened profile and is oriented with a major dimension along said second reference axis, wherein the cross section of said tubular bar has a profile comprising two circular portions (16A, 16C) joined together by two opposed intermediate portions (16B, 16B'), and wherein said two circular portions (16A, 16C) each reproduce an arc of a circle defined by an angle greater than 180°, even more preferably greater than 270°, or else said supporting unit comprises a first tubular bar and a second tubular bar with circular cross section, which are arranged alongside one another along said second reference axis.