A blade system for fans for industrial use, comprising: - a blade , which extends longitudinally along a first reference axis (K) and defines within it a cavity , wherein said blade has a cross section with flattened profile and is oriented with a major dimension (L1) along a second reference axis (H); 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 (L2) along said second reference axis (H); 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 (L3) along said second reference axis (H), wherein the cross section of said tubular bar has a profile comprising two circular portions joined together by two opposed intermediate portions , and wherein said two circular portions 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 (H) . - a blade , which extends longitudinally along a first reference axis (K) and defines within it a cavity , wherein said blade has a cross section with flattened profile and is oriented with a major dimension (L1) along a second reference axis (H); 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 (L2) along said second reference axis (H); 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 (L3) along said second reference axis (H), wherein the cross section of said tubular bar has a profile comprising two circular portions joined together by two opposed intermediate portions , and wherein said two circular portions 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 (H) . said supporting unit comprises a tubular bar , which has a cross section with flattened profile and is oriented with a major dimension (L3) along said second reference axis (H), wherein the cross section of said tubular bar has a profile comprising two circular portions joined together by two opposed intermediate portions , and wherein said two circular portions 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 (H) . <EOS>