Replacement precision-balanced aluminum blades feature AMCA Type B spark-resistant propellers (99-0401-86). Blades are designed specifically for tube axial fans. Note: These fans cannot be used if the environment surrounding them is not always free of flammable gases, vapors, or liquids; combustible dust; or ignitable fibers or flyings. Installation must comply with all local and national safety codes including the National Electrical Code (NEC) and the National Fire Protection Act (NFPA). OSHA complying guards are required when fan is installed within 8 ft. of floor or working level, or within reach of personnel. Review OSHA Codes and UL Standards.